Ebullated bed hydroprocessing systems

ABSTRACT

An ebullated bed hydroprocessing system, and also a method for upgrading a pre-existing ebullated bed hydroprocessing system, involves introducing a colloidal or molecular catalyst, or a precursor composition capable of forming the colloidal or molecular catalyst, into an ebullated bed reactor. The colloidal or molecular catalyst is formed by intimately mixing a catalyst precursor composition into a heavy oil feedstock and raising the temperature of the feedstock to above the decomposition temperature of the precursor composition to form the colloidal or molecular catalyst in situ. The improved ebullated bed hydroprocessing system includes at least one ebullated bed reactor that employs both a porous supported catalyst and the colloidal or molecular catalyst to catalyze hydroprocessing reactions involving the feedstock and hydrogen. The colloidal or molecular catalyst provides catalyst in what would otherwise constitute catalyst free zones within the ebullated bed hydroprocessing system. Asphaltene or other hydrocarbon molecules too large to diffuse into the pores of the supported catalyst can be upgraded by the colloidal or molecular catalyst. A slurry phase reactor may be positioned upstream from one or more ebullated bed reactors or converted from a pre-existing ebullated bed reactor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.11/117,202, filed Apr. 28, 2005, which claims the benefit under 35U.S.C. §119 of U.S. Provisional Application No. 60/566,335, filed Apr.28, 2004, and also U.S. Provisional Application No. 60/566,268, filedApr. 28, 2004, the disclosures of which are incorporated herein in theirentirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The invention involves methods and systems for hydroprocessing heavy oilfeedstocks that include a significant quantity of asphaltenes andfractions boiling above 524° C. (975° F.) to yield lower boiling, higherquality materials. The invention specifically relates to ebullated bedhydroprocessing methods and systems that employ a colloidal or molecularcatalyst and a porous supported catalyst, and methods for upgrading anexisting ebullated bed system, so as to be better suited for upgradinglower quality feedstocks by inhibiting the formation of coke precursorsand sediment and/or extending the life of the supported catalyst.

2. The Relevant Technology

World demand for refined fossil fuels is ever-increasing and willinevitably outstrip the supply of high quality crude oil, whether as aresult of actual shortages or due to the actions of oil cartels. Ineither case, as the price or shortage of crude oil increases there willbe an every-increasing demand to find ways to better exploit lowerquality feedstocks and extract fuel values therefrom. As more economicalways to process lower quality feedstocks become available, suchfeedstocks may possibly catch, or even surpass, higher quality crudeoils, in the not-too-distant future, as the primary source of refinedfossil fuels used to operate automobiles, trucks, farm equipment,aircraft, and other vehicles that rely on internal combustion.

Lower quality feedstocks are characterized as including relatively highquantities of hydrocarbons that have a boiling point of 524° C. (975°F.) or higher. They also contain relatively high concentrations ofsulfur, nitrogen and metals. High boiling fractions typically have ahigh molecular weight and/or low hydrogen/carbon ratio, an example ofwhich is a class of complex compounds collectively referred to as“asphaltenes”. Asphaltenes are difficult to process and commonly causefouling of conventional catalysts and hydroprocessing equipment.

Examples of lower quality feedstocks that contain relatively highconcentrations of asphaltenes, sulfur, nitrogen and metals include heavycrude and oil sands bitumen, as well as bottom of the barrel andresiduum left over from conventional refinery process (collectively“heavy oil”). The terms “bottom of the barrel” and “residuum” (or“resid”) typically refer to atmospheric tower bottoms, which have aboiling point of at least 343° C. (650° F.), or vacuum tower bottoms,which have a boiling point of at least 524° C. (975° F.). The terms“resid pitch” and “vacuum residue” are commonly used to refer tofractions that have a boiling point of 524° C. (975° F.) or greater.

By way of comparison, Alberta light crude contains about 9% by volumevacuum residue, while Lloydminster heavy oil contains about 41% byvolume vacuum residue, Cold Lake bitumen contains about 50% by volumevacuum residue, and Athabasca bitumen contains about 51% by volumevacuum residue. Resid contains even higher concentrations of fractionsthat boil at or above about 343° C. (650° F.), with vacuum tower bottomsalmost exclusively comprising fractions that boil at or above about 524°C. (975° F.).

Converting heavy oil into useful end products requires extensiveprocessing, including reducing the boiling point of the heavy oil,increasing the hydrogen-to-carbon ratio, and removing impurities such asmetals, sulfur, nitrogen and high carbon forming compounds. Examples ofcatalytic hydrocracking processes using conventional supported catalyststo upgrade atmospheric tower bottoms include fixed-bed hydroprocessing,ebullated- or expanded-bed hydroprocessing, and moving-bedhydroprocessing. Noncatalytic processes used to upgrade vacuum towerbottoms include thermal cracking, such as delayed coking andFlexicoking, and solvent extraction. Solvent extraction is quiteexpensive and incapable of reducing the boiling point of the heavy oil.Existing commercial catalytic hydrocracking processes involve rapidcatalyst deactivation and high catalyst cost, making them currentlyunsuitable for hydroprocessing vacuum tower bottoms unless substantiallydiluted with lower boiling, fractions, such as atmospheric towerbottoms. Most existing ebullated bed processes operate at less than 65wt % conversion, while most fixed bed processes have less than about 25wt % conversion.

A major cause of catalyst and equipment fouling is the undesiredformation of coke and sediment, which often results when asphaltenes areheated to the high temperatures required to effect catalytic and thermalcracking. Supported catalysts used in commercial hydrocracking processessuch as fixed-bed and ebullated-bed processes utilize solid supportedcatalysts that include clusters of catalytic sites located within poresor channels in the support material. Most heavy oil feedstocks contain asignificant portion of asphaltene molecules, which are either too largeto enter the pores of the catalyst support or else become trapped withinthe pores. Asphaltene molecules that become trapped in the poresdeactivate the catalyst sites in the blocked pores. In this way, smallerasphaltene molecules can progressively block all catalyst sites,entirely deactivating the catalyst.

Moreover, larger asphaltene molecules form free radicals, just likeother hydrocarbon molecules in the feedstock, but, unlike smallermolecules in the feedstock, are too large to enter the catalyst pores.Because of this, they are generally unable to react with hydrogenradicals located at the catalyst sites. As a result, the largerasphaltene free radicals are free to react with asphaltene and otherfree radicals in the feedstock, thereby forming larger molecules whichcontinue increasing in size that can foul both the catalyst and thehydroprocessing equipment through the formation of coke precursors andsediment. The tendency of asphaltenes to form coke and sedimentincreases as the conversion level of the residuum increases due to themore strenuous conditions required to increase conversion. Theundesirable reactions and fouling involving asphaltene greatly increasethe catalyst and maintenance costs of ebullated-bed and fixed-bedhydrocracking processes. They also render existing commercial processesunsuitable for hydroprocessing vacuum tower bottoms and other very lowquality feedstocks rich in asphaltenes.

Even though ebullated bed hydroprocessing systems are able to operate atsubstantially higher conversion levels than fixed bed systems, ebullatedbed systems likewise suffer from the inability to proportionally convertthe asphaltene fraction at the same conversion level as the heavy oil asa whole. The result of disproportional conversion is a progressivebuildup of asphaltenes in the processed feedstock, with an attendantincrease in the likelihood that coke and sediment will form in thereactor and other processing equipment.

Another problem, particularly acute in the case of ebullated-bedprocesses, involves continued free radical reaction in the catalyst freezones located (i) between the liquid recycle cup and the upper end ofthe expanded catalyst bed, (ii) between the plenum and distributor gridplate at the bottom of the catalyst bed, (iii) outside the pores of theporous supported catalyst within the expanded catalyst bed, and (iv)within the hot separator. The hydrocarbon free radicals generated atelevated temperatures within the ebullated bed are generally able toundergo hydrogenation reactions in the expanded catalyst zone asintended (except for larger asphaltene molecules, as discussed above).However, it is difficult for catalyzed hydrogenation reactions to occurwithin the catalyst free zones. Moreover, as product is withdrawn andsent to the hot separator, hydrocarbon free radicals continue to persistand may be further generated at high feedstock temperatures within thehot separator, which may only be about 2-4° C. (3.6-7.2° F.) less thanthe temperature of the feedstock in the ebullated bed. Because the hotseparator includes no catalyst, free radicals tend to polymerize witheach other rather than being capped by hydrogen through catalytichydrogenation, thereby resulting in the formation of coke precursors andsediment with a high tendency for fouling of the hot separator,downstream heat exchangers, and even the vacuum distillation tower. Theformation of coke precursors and sediment in the hot separator isexacerbated in the case where the feedstock includes a significantconcentration of asphaltenes. Aside from equipment fouling, sedimentsoften lead to instability of residual resid when it is used as a fueloil.

To prevent fouling of the hot separator, the LC-Fining ebullated-bedhydrocracking reactor at Syncrude Canada in the Province of Alberta,Canada has been modified to reduce the temperature of the partiallyupgraded feedstock within the hot separator in order to reduce freeradical formation and associated sediment formation and fouling thatwould otherwise occur in the absence of cooling. This is accomplishedusing an oil quench, in which cooler oil is pumped at elevated pressureto the entrance of the hot separator in order to reduce the temperatureof the reactor product coming into the hot separator.

Another problem associated with conventional ebullated-bed hydrocrackingprocesses is the need to carefully control the temperature and rapidlydisperse the heat that accumulates within stagnant areas throughout theentire bed. Because many hydroconversion reactions are exothermic, andbecause heat can increase the rate of certain reactions, the formationof stagnant spots when the supported catalyst particles are not properlyfluidized within the ebullated bed reactor can result in reactions thatquickly get out of control. Stagnant spots of increased temperature canpromote the formation of coke precursors and sediment, which can bindthe catalyst particles together to form catalyst balls that are tooheavy to be fluidized. Exothermic reactions tend to persist around thecatalyst balls and stagnant zones. One ebullated-bed reactor actuallyblew up due to uncontrolled run-away reactions accelerated by stagnantzones caused by poor distribution of hydrogen, reportedly killingseveral workers in the vicinity of the reactor. Thermocouples aretherefore typically placed throughout the ebullated bed in order tomonitor and maintain an evenly controlled temperature throughout thereactor.

In view of the foregoing, there is an ongoing need to provide improvedebullated bed hydroprocessing systems and/or improve (i.e., modify)existing ebullated bed systems to overcome one or more of the foregoingdeficiencies.

SUMMARY OF THE INVENTION

The present invention relates to ebullated bed hydroprocessing methodsand system for improving the quality of a heavy oil feedstock thatemploy both a porous supported catalyst and a colloidal or molecularcatalyst. The invention also includes methods for upgrading an existingebullated bed hydroprocessing system by augmenting or replacing at leasta portion of the porous supported catalyst with a colloidal or molecularcatalyst. The colloidal or molecular catalyst overcomes at least some ofthe problems associated with the use of porous supported catalysts inupgrading heavy oil feedstocks. These include more effective processingof asphaltene molecules, a reduction in the formation of coke precursorsand sediment, reduced equipment fouling, increased conversion level,enabling the reactor to process a wider range of lower qualityfeedstocks, elimination of catalyst-free zones in the ebullated bedreactor and downstream processing equipment, longer operation in betweenmaintenance shut downs, and more efficient use of the supported catalystif used in combination with the colloidal or molecular catalyst.Reducing the frequency of shutdown and startup of process vessels meansless pressure and temperature cycling of process equipment, and itsignificantly increases the process safety and extends the useful lifeof expensive equipment.

Conventional ebullated bed hydroprocessing systems typically include oneor more ebullated bed reactors that comprise a reaction chamber, a portat the bottom of the reaction chamber through which a heavy oilfeedstock and pressurized hydrogen gas are introduced, a port at the topof the reaction chamber through which fresh catalyst is introduced, arecycle cup and conduit in the center of the reaction chamber, anexpanded catalyst zone, an ebullating pump that circulates the reactorliquid down through the recycle cup and conduit and up through theexpanded catalyst zone, a first catalyst free zone at the reactor bottom(or plenum), a second catalyst free zone above the expanded catalystzone, a port at the top of the reaction chamber through which anupgraded feedstock is withdrawn from the second catalyst free zone, anda port at the bottom of the reaction chamber through which spentcatalyst is withdrawn. Circulation of the heavy oil feedstock upwardsthrough the expanded catalyst zone maintains the solid supportedcatalyst in an expanded, or fluidized state. It also helps equalize thetemperature of the feedstock throughout the reaction chamber.

All or substantially all of the beneficial upgrading reactions occurwithin the expanded catalyst zone since that is the only place withinthe ebullated bed reactor where the heavy oil feedstock, hydrogen andporous supported catalyst exist together. The heavy oil molecules withinthe feedstock undergo thermal cracking within the ebullated bed reactorto form free radicals of reduced chain length. The free radicals diffuseinto the pores of the porous supported catalyst where the free radicalends are catalytically reacted with hydrogen, thereby forming stablehydrocarbons of reduced molecular weight and boiling point.Unfortunately, heavy oil molecules within the feedstock can continueundergoing thermal cracking reactions in the catalyst free zones so asto form free radicals that have the potential of reacting with otherfree radicals to produce coke precursors and sediment within theebullated bed reactor and/or within downstream processing equipment.Likewise, larger molecules that are too large to diffuse into the poresof the ebullated bed catalyst.

Moreover, asphaltenes and/or other heavy oil molecules that are toolarge to enter the pores of the supported catalyst can form cokeprecursors and sediment even within the expanded catalyst zone,potentially fouling and/or prematurely deactivating the catalyst (e.g.,by plugging the pores of the catalyst and/or agglomerating poroussupported catalyst particles together to form catalyst balls).Asphaltene free radicals often also leave behind trace metals such asvanadium and nickel in the catalyst pores, gradually reducing the porediameter and preventing further access by other hydrocarbon molecules orradicals. For the foregoing reasons, it is very difficult to upgradeheavy oil feedstocks rich in asphaltenes (e.g., vacuum tower bottoms)using conventional ebullated bed hydroprocessing systems because theytend to quickly foul and/or deactivate such systems.

The present invention provides improved ebullated bed hydroprocessingmethods and systems that more effectively process lower quality heavyoil feedstocks. The ebullated bed hydroprocessing methods and systems ofthe invention employ a dual hydroprocessing catalyst system comprising acolloidal or molecular catalyst and a porous supported catalyst. Thecolloidal or molecular catalyst and porous supported catalyst may beused together within one or more ebullated bed reactors. Alternatively,the colloidal or molecular catalyst may be used separately within one ormore slurry phase reactors and then together with the porous supportedcatalyst within one or more ebullated bed reactors. One or more hotseparators may be positioned at various points within the system inorder to remove gases and volatile liquids from the non-volatile liquidfraction, which is then processed in one or more downstreamhydroprocessing reactors. A guard bed may be used to remove metals andother impurities and/or the colloidal or molecular catalyst prior tofurther processing of the feedstock into final usable products. Where itis desired to recycle a heavy resid fraction back through thehydroprocessing system it may be advantageous to leave the colloidal ormolecular catalyst within the resid fraction. The colloidal or molecularcatalyst generally does not become deactivated and can be used tocatalyze beneficial upgrading reactions within the recycled residfraction without having to add new catalyst.

According to one embodiment, a colloidal or molecular catalyst is formedand/or a well-dispersed catalyst precursor composition is incorporatedwithin a heavy oil feedstock prior to introducing the feedstock into atleast one of an ebullated bed or slurry phase reactor. Thewell-dispersed catalyst precursor composition is able to form thecolloidal or molecular catalyst in situ in the feed heaters and/orwithin the ebullated bed or slurry phase reactor. One benefit of thecolloidal or molecular catalyst is that it provides catalytic activityin addition to the porous supported catalyst.

In the case of heavy oil feedstocks that include asphaltenes, asignificant portion of the colloidal-sized particles or molecules of thepolar hydroprocessing catalyst become associated with the morehydrophilic asphaltene molecules. As the asphaltene molecules form freeradicals during thermal cracking, the closely associated colloidalcatalyst particles or molecules catalyze a reaction between theasphaltene radicals and hydrogen, thereby preferentially promotingbeneficial upgrading reactions to form smaller hydrocarbon moleculesthat contain less sulfur instead of forming coke precursors andsediment. As a result, the asphaltene fraction found in heavy oilfeedstocks can be upgraded into more usable materials along with otherhydrocarbons in the feedstock rather than simply being a coke andsediment precursor that is, at best, a waste product that must bedisposed of and, at worst, a nemesis that can quickly deactivate theporous supported catalyst and/or foul the ebullated bed hydroprocessingsystem, requiring substantially greater quantities of catalyst and/orcostly shut downs and clean-up operations. Repeatedly shutting downpressurized vessels involving high temperature and high pressurecyclings can greatly increase the risk of damaging the mechanicalintegrity of the equipment and reduce their operating life.

When used in combination with a porous supported catalyst in anebullated bed reactor, the colloidal or molecular catalyst promotescatalytic upgrading reactions rather than detrimental reactions betweenhydrocarbon free radicals within what would otherwise constitute thecatalyst free zones of the ebullated bed reactor and downstreamprocessing equipment. The colloidal or molecular catalyst also promotesbeneficial upgrading reactions involving asphaltenes or otherhydrocarbon molecules that are too large to diffuse into the pores ofthe porous supported catalyst. This reduces or eliminates the incidenceof catalyst fouling, such as plugging the catalyst pores and/or catalystballing, and/or formation of coke precursors and sediment that mightotherwise foul the ebullated bed reactor and downstream equipment.

When the colloidal or molecular catalyst is used in a slurry phasereactor upstream from an ebullated bed reactor, upgrading reactionswithin the slurry phase reactor reduce the quantity of asphaltenes orother larger hydrocarbon molecules that otherwise could not enter thepores of the supported catalyst within the ebullated bed reactor. Inthis way, the colloidal or molecular catalyst can be employed topreliminarily upgrade a lower quality heavy oil feedstock into a higherquality feedstock comprising smaller hydrocarbon molecules of lowermolecular weight that can be more effectively hydroprocessed by theporous supported catalyst of the ebullated bed reactor. This reducesfouling of the ebullated bed reactor and downstream equipment andincreases the lifespan of the porous supported catalyst.

The methods and systems according to the invention may employ otherprocessing equipment as desired upstream and/or downstream from one ormore ebullated bed reactors. Examples of other processing equipment thatmay be incorporated within the ebullated bed hydroprocessing systems ofthe invention include one or more of a preheating chamber, such as forcausing the well dispersed catalyst precursor composition to decomposeand/or for causing the heavy oil feedstock to liberate sulfur that cancombine with the metal liberated from the catalyst precursorcomposition, a slurry phase reactor, a fixed bed reactor, an atmosphericdistillation tower, a vacuum distillation tower, a scrubber, an aqueouswashing system, and conduits and channels for transporting the feedstockfrom one location in the system to another.

The colloidal or molecular catalyst within the heavy oil feedstock istypically formed in situ within the heavy oil feedstock prior to, orupon introducing the feedstock into an ebullated bed and/or slurry phasereactor. According to one embodiment, an oil soluble catalyst precursorcomposition comprising an organo-metallic compound or complex is blendedwith the heavy oil feedstock containing sulfur bearing molecules andthoroughly mixed in order to achieve a very high dispersion of theprecursor composition within the feedstock prior to formation of thecatalyst. An exemplary catalyst precursor composition is a molybdenum2-ethylhexanoate complex containing approximately 15% by weightmolybdenum.

In order to ensure thorough mixing of the precursor composition withinthe feedstock, the catalyst precursor composition is preferablypreblended with a hydrocarbon oil diluent (e.g., vacuum gas oil, decantoil, cycled oil, or light gas oil) to create a diluted precursormixture, which is thereafter blended with the heavy oil feedstock. Thedecomposition temperature of the catalyst precursor composition isselected so as to be sufficiently high so that the catalyst precursorcomposition resists substantial premature decomposition before intimatemixing of the catalyst precursor composition within the feedstock hasbeen achieved. Subsequent heating of the feedstock to a temperaturesufficient to cause the release of hydrogen sulfide from sulfur-bearinghydrocarbon molecules, either before or upon commencing hydroprocessing,causes the catalyst precursor composition that has been intimately mixedwith the feedstock to yield individual metal sulfide catalyst moleculesand/or extremely small particles that are colloidal in size (i.e., lessthan 100 nm, preferably less than about 10 nm, more preferably less thanabout 5 nm, and most preferably less than about 1 nm).

Once formed, the metal sulfide catalyst compound, being dissociated fromthe oil soluble portion of the catalyst precursor, is highly polar. Onthe other hand, oil feedstocks are very hydrophobic, making itimpossible to disperse larger hydrophilic metal sulfide catalystparticles into smaller-sized particles within the feedstock, let aloneso as to yield a colloidal or molecular dispersion of catalyst. This istrue whether the metal catalyst compound is added directly to the oilfeedstock as a solid powder or as part of an aqueous solution instead ofusing an oil soluble catalyst precursor composition as in the presentinvention to form the catalyst compound in situ within the feedstock. Itis for this reason that the oil soluble precursor composition isintimately mixed with the feedstock before decomposition of the catalystprecursor composition and formation of the catalyst compound.

If the oil soluble catalyst precursor composition is well mixedthroughout the heavy oil feedstock before decomposition, the metalcatalyst atoms and/or metal catalyst compounds will be physicallyseparated from each other and surrounded by the heavy oil feedstockmolecules, which is believed to prevent or inhibit substantialagglomeration. It has been found that preblending the catalyst precursorcomposition with a hydrocarbon diluent prior to blending the resultingdiluted precursor mixture within the feedstock greatly aids in ensuringthat thorough blending of the precursor composition within the feedstockoccurs before decomposition of the precursor composition to yield thecatalyst, particularly in the case of large-scale industrialapplications. The result of thorough mixing is that all, or asubstantial portion, of the catalyst precursor composition is convertedinto individual metal sulfide molecules, or particles colloidal in size,instead of larger metal sulfide particles comprising a large number ofmetal sulfide compounds joined together. On the other hand, failure tointimately blend the oil soluble precursor composition into thefeedstock before decomposition of the precursor results in the formationof larger catalyst particles (i.e., micron-sized or greater) comprisinga relatively large number of metal sulfide molecules joined togetherrather than a molecular or colloidal dispersion of the metal sulfidecatalyst.

Notwithstanding the generally hydrophobic nature of heavy oilfeedstocks, because asphaltene molecules generally have a large numberof oxygen, sulfur and nitrogen functional groups, as well as associatedmetal constituents such as nickel and vanadium, the asphaltene fractionis significantly less hydrophobic and more hydrophilic than otherhydrocarbons within the feedstock. Asphaltene molecules thereforegenerally have a greater affinity for the polar metal sulfide catalyst,particularly when in a colloidal or molecular state, compared to morehydrophobic hydrocarbons in a heavy oil feedstock. As a result, asignificant portion of the polar metal sulfide molecules or colloidalparticles tend to become associated with the more hydrophilic and lesshydrophobic asphaltene molecules compared to the more hydrophobichydrocarbons in the feedstock. The close proximity of the catalystparticles or molecules to the asphaltene molecules helps promotebeneficial upgrading reactions involving free radicals formed throughthermal cracking of the asphaltene fraction. This phenomenon isparticularly beneficial in the case of heavy oils that have a relativelyhigh asphaltene content, which are otherwise difficult, if notimpossible, to upgrade using conventional hydroprocessing techniques dueto the tendency of asphaltenes to deactivate porous supported catalystsand deposit coke and sediments on or within the processing equipment. Inthe case of conventional ebullated bed hydroprocessing systems, theasphaltene content may generally not exceed 10% by volume of thefeedstock.

According to one embodiment, metal catalyst atoms liberated from theorgano-metallic precursor compound or complex react with sulfurliberated from the heavy oil feedstock during heating to yield metalcatalyst compounds that comprise one or more types of metal sulfides. Anon-limiting example of a useful metal sulfide catalyst that may beemployed in the methods and systems according to the invention ismolybdenum disulfide. A non-limiting example of a catalyst precursorcomposition used to form molybdenum disulfide is molybdenum 2-ethylhexanoate.

The molecular or colloidal catalyst generally never becomes deactivatedbecause it is not contained within the pores of a support material.Moreover, because of intimate contact with the heavy oil molecules, themolecular or colloidal catalyst particles can rapidly catalyze ahydrogenation reaction between hydrogen atoms and free radicals formedfrom the heavy oil molecules. Although the molecular or colloidalcatalyst leaves the reactor with the upgraded product, it is constantlybeing replaced with fresh catalyst contained in the incoming feedstock.As a result, process conditions, throughput and conversion levels remainsignificantly more constant over time compared to ebullated bedprocesses that utilize a porous supported catalyst as the solehydroprocessing catalyst. Moreover, because the molecular or colloidalcatalyst is more freely dispersed throughout the feedstock, includingbeing intimately associated with asphaltenes, conversion levels andthroughput are significantly or substantially increased compared toconventional ebullated bed hydroprocessing systems.

The more uniformly dispersed molecular or colloidal catalyst is alsoable to more evenly distribute the catalytic reaction sites throughoutthe reaction chamber and feedstock. This reduces the tendency for freeradicals to react with one another to form coke precursor molecules andsediment compared to conventional ebullated bed reactors that only use arelatively large (e.g., ¼″×⅛″ or ¼″× 1/16″) (6.35 mm×3.175 mm or 6.35mm×1.5875 mm) supported catalyst, wherein the heavy oil molecules mustdiffuse into the pores of catalyst support to reach the active catalystsites.

In another aspect of the invention, an existing ebullated bedhydroprocessing system can be upgraded by augmenting or at leastpartially replacing the supported catalyst with the molecular orcolloidal catalyst described herein. Ebullated bed hydroprocessingsystems typically cost millions of dollars to build. Rather thandismantling such systems, or building entirely new hydroprocessingsystems at great cost to accommodate low quality heavy oil feedstocksthat are rich in asphaltenes and/or high boiling fractions (e.g., above975° F.), the present invention provides a method for modifying apre-existing ebullated bed hydroprocessing system so that it can moreeffectively process lower quality heavy oil feedstocks.

The modifying or upgrading of a pre-existing ebullated bed system isaccomplished by incorporating a colloidal or molecular catalyst and/or awell-dispersed catalyst precursor composition within the heavy oilfeedstock prior to introducing the feedstock into the ebullated bedreactor. The well-dispersed catalyst precursor composition is able toform the colloidal or molecular catalyst in situ in the feed heatersand/or within the ebullated bed reactor. This provides catalyticactivity within what previously constituted catalyst free zones withinthe ebullated bed reactor and downstream processing equipment prior toupgrading according to the invention. This promotes beneficial upgradingreactions within the former catalyst free zones rather than detrimentalreactions between hydrocarbon free radicals.

According to one embodiment of the invention, a pre-existing ebullatedbed hydroprocessing reactor system is upgraded by incorporating acolloidal or molecular catalyst within the heavy oil feedstock whilemaintaining the same quantity of porous supported catalyst employedpreviously. Incorporating the colloidal or molecular catalyst within theheavy oil feedstock would be expected to increase the life of the poroussupported catalyst, thereby reducing the rate at which spent supportedcatalyst must be replaced. This has the beneficial effect of reducingthe porous supported catalyst requirement. The more evenly distributedcatalytic sites also increase the conversion level, while reducing oreliminating the tendency of free radicals to react together to form cokeprecursors and sediment.

According to another embodiment of the invention, a pre-existingebullated bed hydroprocessing reactor system is upgraded byincorporating a colloidal or molecular catalyst within the heavy oilfeedstock while reducing the quantity of the porous supported catalystwithin the ebullated bed reactor. Because of the additive catalyticeffect of the colloidal or molecular catalyst, less porous supportedcatalyst will generally be required to maintain a desired conversionlevel. The amount of porous supported catalyst may be reduced from aninitial threshold quantity to a final reduced quantity, either abruptlyor gradually over time. The quantity of porous supported catalyst mayalso be incrementally reduced to one or more intermediate plateaus thatare maintained for a desired period of time before finally reaching thefinal reduced quantity.

Alternatively, the amount of porous supported catalyst and/or colloidalor molecular catalyst may be periodically reduced or increased in orderto maintain an optimum ratio of the colloidal or molecular catalyst tothe porous supported catalyst for a particular grade of heavy oilfeedstock. This may be beneficial in the case where the quality of theheavy oil feedstock fluctuates from time to time. This allows theupgraded ebullated bed system to be altered or fine tuned depending onthe chemical make-up of the feedstock that is to be processed at anygiven time.

In the case where a pre-existing hydroprocessing system includes morethan one ebullated bed reactor in sequence, it is within the scope ofthe invention to upgrade each ebullated bed reactor in the same way(e.g., by maintaining a constant level of the porous supported catalystin each reactor or by reducing the supported catalyst by the same amountin each ebullated bed reactor). It is also within the scope of theinvention to utilize or maintain varying quantities of porous supportedcatalyst among the different ebullated bed reactors. It is also withinthe scope of the invention to remove at least a portion of the colloidalor molecular catalyst, other metals, and/or impurities from the upgradedfeedstock before introducing it into a subsequent ebullated bed reactordownstream, e.g., by means of a “guard bed”. Alternatively, supplementalcolloidal or molecular catalyst can be added to the upgraded feedstockand/or the downstream reactor(s) to offset possible catalyst removal bythe porous supported catalyst in the upstream reactor(s).

It is also within the scope of the invention to upgrade a pre-existingebullated bed reactor by eliminating the porous supported catalystentirely and replacing it with the colloidal or molecular catalyst. Inthis case, the “upgraded” ebullated bed reactor within the ebullated bedsystem may no longer technically be an “ebullated bed reactor” but a“slurry phase reactor”. By way of example and not limitation, a firstebullated bed reactor within a hydroprocessing system that includesmultiple ebullated bed reactors may be upgraded by eliminating theporous supported catalyst entirely, while one or more downstreamebullated bed reactors may still include at least a portion of theoriginal quantity of porous supported catalyst employed initially.Alternatively, or in addition, one or more new slurry phase reactorscomprising a heavy oil feedstock and a colloidal or molecular catalystas liquid phase and hydrogen gas as gaseous phase may be constructedupstream relative to one or more ebullated bed reactors, including anebullated bed reactor that has been converted into a slurry phasereactor.

An upgraded ebullated bed hydroprocessing system according to theinvention may include processing and handling equipment upstream anddownstream from the one or more ebullated bed reactors as needed toyield a desired hydroprocessing system. Such other processing andhandling equipment may include, for example, one or more of a preheatingchamber, such as for causing the well dispersed catalyst precursorcomposition to decompose and/or for causing the heavy oil feedstock toliberate sulfur that can combine with the metal liberated from thecatalyst precursor composition, a hot separator, a slurry phase reactor,a fixed bed reactor, a guard bed, an atmospheric distillation tower, avacuum distillation tower, a scrubber, an aqueous washing system, andconduits and channels for transporting the feedstock from one locationin the system to another.

These and other advantages and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of thepresent invention, a more particular description of the invention willbe rendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope. The invention willbe described and explained with additional specificity and detailthrough the use of the accompanying drawings, in which:

FIG. 1 depicts a hypothetical chemical structure for an asphaltenemolecule;

FIGS. 2A and 2B are schematic diagrams that illustrate exemplaryebullated bed reactors that may be incorporated into improved ebullatedbed hydroprocessing systems according to the invention;

FIG. 2C is a schematic diagram that illustrates an exemplary ebullatedbed hydroprocessing system comprising multiple ebullated bed reactorsthat may be incorporated into or upgraded to yield an improved ebullatedbed hydroprocessing system according to the invention;

FIG. 3 is a flow diagram that schematically illustrates an exemplaryprocess for preparing a heavy oil feedstock to include a molecular orcolloidal catalyst dispersed therein;

FIG. 4 schematically illustrates catalyst molecules or colloidal-sizedcatalyst particles associated with asphaltene molecules;

FIGS. 5A and 5B schematically depict top and side views of a molybdenumdisulfide crystal approximately 1 nm in size;

FIG. 6 is a schematic diagram of an exemplary ebullated bedhydroprocessing system according to the invention that includes a slurryphase reactor, an ebullated bed reactor, and a hot separator;

FIG. 7A-7C are block diagrams that illustrate exemplary ebullated bedhydroprocessing systems according to the invention;

FIGS. 8A-8D are flow diagrams that illustrate exemplary methods forupgrading a pre-existing ebullated bed hydroprocessing system;

FIG. 9 is a chart comparing the asphaltene conversions using a colloidalor molecular catalyst versus using a porous supported catalyst;

FIG. 10 is a schematic diagram of a pilot slurry phase/ebullated bedhydroprocessing system used to compare a colloidal or molecular catalystaccording to the invention and a conventional ebullated bed catalyst;

FIG. 11 is a chart comparing increases in pressure drop across thesecond pilot ebullated bed reactor over time for test runs using eithera porous supported catalyst by itself or in combination with a colloidalor molecular catalyst;

FIG. 12 is a chart depicting resid conversion at various hours on streamfor test runs using either a porous supported catalyst by itself or incombination with a colloidal or molecular catalyst;

FIG. 13 is a chart comparing asphaltene conversion at various hours onstream for test runs using either a porous supporting catalyst by itselfor in combination with a colloidal or molecular catalyst;

FIG. 14 is a chart comparing desulfurization at various hours on streamfor test runs using either a porous supported catalyst by itself or incombination with a colloidal or molecular catalyst;

FIG. 15 is a chart comparing increases in pressure drop across thesecond pilot ebullated bed reactor over time for test runs using eithera porous supported catalyst by itself or in combination with a colloidalor molecular catalyst;

FIG. 16 is a chart comparing resid conversion at various hours on streamfor test runs using either a porous supported catalyst by itself or incombination with the colloidal or molecular catalyst;

FIG. 17 is a chart comparing C₇ asphaltene conversion at various hourson stream for test runs using either a porous supported catalyst byitself or in combination with a colloidal or molecular catalyst.

FIG. 18 is a chart comparing hot separator bottom API gravity at varioushours on stream for test runs using either a porous supported catalystby itself or in combination with a colloidal or molecular catalyst.

FIG. 19 is a chart comparing unconverted resid API gravity at varioushours on stream for test runs using either a porous supported catalystby itself or in combination with a colloidal or molecular catalyst.

FIG. 20 is a chart comparing IP-375 sediment in hot separator bottoms atvarious hours on stream for test runs using either a porous supportedcatalyst by itself or in combination with a colloidal or molecularcatalyst;

FIG. 21 is a chart comparing the asphaltene concentration in the hotseparator bottoms at various hours on stream or test runs using either aporous supported catalyst by itself or in combination with a colloidalor molecular catalyst; and

FIG. 22 is a chart comparing the MCR in hot separator bottoms at varioushours on stream for test runs using either a porous supported catalystby itself or in combination with a colloidal or molecular catalyst.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Introduction andDefinitions

The present invention relates to ebullated bed hydroprocessing methodsand systems for improving the quality of a heavy oil feedstock. Suchmethods and systems employ a dual catalyst system that includes amolecularly- or colloidally-dispersed hydroprocessing catalyst and aporous supported catalyst. The ebullated bed hydroprocessing methods andsystems of the invention more effectively process asphaltene molecules,reduce or eliminate the formation of coke precursors and sediment,reduce equipment fouling, increase conversion level, eliminatecatalyst-free zones that would otherwise exist in conventional ebullatedbed reactors and downstream processing equipment, and more efficientlyuse the porous supported catalyst.

The invention also relates to methods for upgrading a pre-existingebullated bed hydroprocessing system. This involves augmenting orreplacing at least a portion of the porous supported catalyst in thepre-existing ebullated bed system with a molecular or colloidalcatalyst.

The terms “colloidal catalyst” and “colloidally-dispersed catalyst”shall refer to catalyst particles having a particle size that iscolloidal in size, e.g., less than about 100 nm in diameter, preferablyless than about 10 nm in diameter, more preferably less than about 5 nmin diameter, and most preferably less than about 1 nm in diameter. Theterm “colloidal catalyst” includes, but is not limited to, molecular ormolecularly-dispersed catalyst compounds.

The terms “molecular catalyst” and “molecularly-dispersed catalyst”shall refer to catalyst compounds that are essential “dissolved” orcompletely dissociated from other catalyst compounds or molecules in aheavy oil hydrocarbon feedstock, non-volatile liquid fraction, bottomsfraction, resid, or other feedstock or product in which the catalyst maybe found. It shall also refer to very small catalyst particles that onlycontain a few catalyst molecules joined together (e.g., 15 molecules orless).

The terms “residual catalyst”, “residual molecular catalyst” and“residual colloidal catalyst” shall refer to catalyst molecules orcolloidal particles that remain with an upgraded feedstock or materialwhen transferred from one vessel to another (e.g., from a hydrocrackingreactor to a hot separator, another hydroprocessing reactor, ordistillation tower).

The term “conditioned feedstock” shall refer to a heavy oil feedstockinto which an oil soluble catalyst precursor composition has beencombined and mixed sufficiently so that, upon decomposition of thecatalyst precursor and formation of the catalyst, the catalyst willcomprise a colloidal or molecular catalyst dispersed within thefeedstock.

The term “hydrocracking” shall refer to a process whose primary purposeis to reduce the boiling range of a heavy oil feedstock and in which asubstantial portion of the feedstock is converted into products withboiling ranges lower than that of the original feedstock. Hydrocrackinggenerally involves fragmentation of larger hydrocarbon molecules intosmaller molecular fragments having a fewer number of carbon atoms and ahigher hydrogen-to-carbon ratio. The mechanism by which hydrocrackingoccurs typically involves the formation of hydrocarbon free radicalsduring fragmentation followed by capping of the free radical ends ormoieties with hydrogen. The hydrogen atoms or radicals that react withhydrocarbon free radicals during hydrocracking are generated at or byactive catalyst sites.

The term “hydrotreating” shall refer to a more mild operation whoseprimary purpose is to remove impurities such as sulfur, nitrogen,oxygen, halides, and trace metals from the feedstock and saturateolefins and/or stabilize hydrocarbon free radicals by reacting them withhydrogen rather than allowing them to react with themselves. The primarypurpose is not to change the boiling range of the feedstock.Hydrotreating is most often carried out using a fixed bed reactor,although other hydroprocessing reactors can also be used forhydrotreating, an example of which is an ebullated bed hydrotreater.

Of course, “hydrocracking” may also involve the removal of sulfur andnitrogen from a feedstock as well as olefin saturation and otherreactions typically associated with “hydrotreating”. The terms“hydroprocessing” and “hydroconversion” shall broadly refer to both“hydrocracking” and “hydrotreating” processes, which define oppositeends of a spectrum, and everything in between along the spectrum.

The terms “solid supported catalyst”, “porous supported catalyst” and“supported catalyst” shall refer to catalysts that are typically used inconventional ebullated bed and fixed bed hydroprocessing systems,including catalysts designed primarily for hydrocracking orhydrodemetallization and catalysts designed primarily for hydrotreating.Such catalysts typically comprise (i) a catalyst support having a largesurface area and numerous interconnected channels or pores of unevendiameter and (ii) fine particles of an active catalyst such as sulfidesof cobalt, nickel, tungsten, and molybdenum dispersed within the pores.For example a heavy oil hydrocracking catalyst manufactured by CriterionCatalyst, Criterion 317 trilube catalyst, has a bi-modal pore sizedistribution, with 80% of the pores ranging between 30 to 300 Angstromswith a peak at 100 Angstroms and 20% of the pores ranging between 1000to 7000 Angstroms with a peak at 4000 Angstroms. The pores for the solidcatalyst support are of limited size due to the need for the supportedcatalyst to maintain mechanical integrity to prevent excessive breakdownand formation of excessive fines in the reactor. Supported catalysts arecommonly produced as cylindrical pellets or spherical solids.

The term “heavy oil feedstock” shall refer to heavy crude, oils sandsbitumen, bottom of the barrel and resid left over from refineryprocesses (e.g., visbreaker bottoms), and any other lower qualitymaterial that contains a substantial quantity of high boilinghydrocarbon fractions (e.g., that boil at or above 343° C. (650° F.),more particularly at or above about 524° C. (975° F.)), and/or thatinclude a significant quantity of asphaltenes that can deactivate asolid supported catalyst and/or cause or result in the formation of cokeprecursors and sediment. Examples of heavy oil feedstocks include, butare not limited to, Lloydminster heavy oil, Cold Lake bitumen, Athabascabitumen, atmospheric tower bottoms, vacuum tower bottoms, residuum (or“resid”), resid pitch, vacuum residue, and nonvolatile liquid fractionsthat remain after subjecting crude oil, bitumen from tar sands,liquefied coal, oil shale, or coal tar feedstocks to distillation, hotseparation, and the like and that contain higher boiling fractionsand/or asphaltenes.

The term “hydrocracking reactor” shall refer to any vessel in whichhydrocracking (i.e., reducing the boiling range) of a feedstock in thepresence of hydrogen and a hydrocracking catalyst is the primarypurpose. Hydrocracking reactors are characterized as having an inputport into which a heavy oil feedstock and hydrogen can be introduced, anoutput port from which an upgraded feedstock or material can bewithdrawn, and sufficient thermal energy so as to form hydrocarbon freeradicals in order to cause fragmentation of larger hydrocarbon moleculesinto smaller molecules. Examples of hydrocracking reactors include, butare not limited to, slurry phase reactors (i.e., a two phase, gas-liquidsystem), ebullated bed reactors (i.e., a three phase, gas-liquid-solidsystem), fixed bed reactors (i.e., a three-phase system that includes aliquid feed trickling downward over a fixed bed of solid supportedcatalyst with hydrogen typically flowing concurrently, but possiblycountercurrently in some cases).

The term “hydrocracking temperature” shall refer to a minimumtemperature required to effect significant hydrocracking of a heavy oilfeedstock. In general, hydrocracking temperatures will preferably fallwithin a range of about 410° C. (770° F.) to about 460° C. (860° F.),more preferably in a range of about 420° C. (788° F.) to about 450° C.(842° F.), and most preferably in a range of about 430° C. (806° F.) toabout 445° C. (833° F.). It will be appreciated that the temperaturerequired to effect hydrocracking may vary depending on the propertiesand chemical make up of the heavy oil feedstock. Severity ofhydrocracking may also be imparted by varying the space velocity of thefeedstock, i.e., the residence time of feedstock in the reactor, whilemaintaining the reactor at a fixed temperature. Milder reactortemperature and longer feedstock space velocity are typically requiredfor heavy oil feedstock with high reactivity and/or high concentrationof asphaltenes.

The term “gas-liquid slurry phase hydrocracking reactor” shall refer toa hydroprocessing reactor that includes a continuous liquid phase and agaseous disperse phase which forms a “slurry” of gaseous bubbles withinthe liquid phase. The liquid phase typically comprises a hydrocarbonfeedstock that may contain a low concentration of a colloidal catalystor molecular-sized catalyst, and the gaseous phase typically compriseshydrogen gas, hydrogen sulfide, and vaporized low boiling pointhydrocarbon products. The term “gas-liquid-solid, 3-phase slurryhydrocracking reactor” is used when a solid catalyst is employed alongwith liquid and gas. The gas may contain hydrogen, hydrogen sulfide andvaporized low boiling hydrocarbon products. The term “slurry phasereactor” shall broadly refer to both type of reactors (e.g., those witha colloidal or molecular catalyst, those with a micron-sized or largerparticulate catalyst, and those that include both). In most cases, itshall refer to a reactor that at least includes a colloidal or molecularcatalyst. An exemplary slurry phase reactor is disclosed in U.S.application Ser. No. 10/225,937, filed Aug. 22, 2002, and entitled“APPARATUS FOR HYDROCRACKING AND/OR HYDROGENATING FOSSIL FUELS”, thedisclosure of which is incorporated herein by specific reference.

The term “asphaltene” shall refer to the fraction of a heavy oilfeedstock that is typically insoluble in paraffinic solvents such aspropane, butane, pentane, hexane, and heptane and that includes sheetsof condensed ring compounds held together by hetero atoms such assulfur, nitrogen, oxygen and metals. Asphaltenes broadly include a widerange of complex compounds having anywhere from 80 to 160,000 carbonatoms, with predominating molecular weights, as determined by solutiontechniques, in the 5000 to 10,000 range. About 80-90% of the metals inthe crude oil are contained in the asphaltene fraction which, togetherwith a higher concentration of non-metallic hetero atoms, renders theasphaltene molecules more hydrophilic and less hydrophobic than otherhydrocarbons in crude. A hypothetical asphaltene molecule structuredeveloped by A. G. Bridge and co-workers at Chevron is depicted in FIG.1.

The terms “upgrade”, “upgrading” and “upgraded”, when used to describe afeedstock that is being or has been subjected to hydroprocessing, or aresulting material or product, shall refer to one or more of a reductionin the molecular weight of the feedstock, a reduction in the boilingpoint range of the feedstock, a reduction in the concentration ofasphaltenes, a reduction in the concentration of hydrocarbon freeradicals, and/or a reduction in the quantity of impurities, such assulfur, nitrogen, oxygen, halides, and metals.

II. Ebullated Bed Hydroprocessing Methods and System

A. Exemplary Ebullated Bed Reactors and Systems

FIGS. 2A and 2B schematically depict conventional ebullated bed reactorsthat are used to process a hydrocarbon feedstock and that can beupgraded according to the invention. FIG. 2A schematically depicts anebullated bed reactor 10 used in the LC-Fining hydrocracking systemdeveloped by C-E Lummus. Ebullated bed reactor 10 includes an input port12 at the bottom through which a feedstock 14 and pressurized hydrogengas 16 are introduced and an output port 18 at the top through which anupgraded feedstock 20 is withdrawn.

Ebullated bed reactor 10 further includes an expanded catalyst zone 22comprising a porous supported catalyst 24 that is maintained in anexpanded or fluidized state against the force of gravity by upwardmovement of feedstock and gas (schematically depicted as bubbles 25)through the ebullated bed reactor 10. The lower end of the expandedcatalyst zone 22 is defined by a distributor grid plate 26, whichseparates the expanded catalyst zone 22 from a lower supported catalystfree zone 28 located between the bottom of the ebullated bed reactor 10and the distributor grid plate 26. The distributor grid plate 26distributes the hydrogen gas and feedstock even across the reactor andprevents the supported catalyst 24 from falling by the force of gravityinto the lower supported catalyst free zone 28. The upper end of theexpanded catalyst zone 22 is the height at which the downward force ofgravity begins to equal or exceed the uplifting force of the upwardlymoving feedstock and gas through the ebullated bed reactor 10 as thesupported catalyst 24 reaches a given level of expansion or separation.Above the expanded catalyst zone 22 is an upper supported catalyst freezone 30.

Feedstock within the ebullated bed reactor 10 is continuouslyrecirculated from the upper supported catalyst free zone 30 to the lowersupported catalyst free zone 28 of the ebullated bed reactor 10 by meansof a recycling channel 32 disposed in the center of the ebullated bedreactor 10 in communication with an ebullating pump 34 disposed at thebottom of the ebullated bed reactor 10. At the top of the recyclingchannel 32 is a funnel-shaped recycle cup 36 through which feedstock isdrawn from the upper supported catalyst free zone 30. The feedstockdrawn downward through the recycling channel 32 enters the lowercatalyst free zone 28 and then passes up through the distributor gridplate 26 and into the expanded catalyst zone 22, where it is blendedwith the feedstock 14 and hydrogen gas 16 entering the ebullated bedreactor 130 through the input port 12. Continuously circulating blendedfeedstock upward through the ebullated bed reactor 10 advantageouslymaintains the supported catalyst 24 in an expanded or fluidized statewithin the expanded catalyst zone 22, minimizes channeling, controlsreaction rates, and keeps heat released by the exothermic hydrogenationreactions to a safe level.

Fresh supported catalyst 24 is introduced into the ebullated bed reactor10, more specifically the expanded catalyst zone 22, through a catalystinput tube 38 that passes through the top of the ebullated bed reactor10 and directly into the expanded catalyst zone 22. Spent supportedcatalyst 24 is withdrawn from the expanded catalyst zone 22 through acatalyst withdrawal tube 40 that passes from a lower end of the expandedcatalyst zone 22 through both the distributor grid plate 26 and thebottom of the ebullated bed reactor 10. It will be appreciated that thecatalyst withdrawal tube 40 is unable to differentiate between fullyspent catalyst, partially spent but active catalyst, and fresh catalystsuch that a random distribution of supported catalyst 24 is withdrawnfrom the ebullated bed reactor 10 as “spent” catalyst. This has theeffect of wasting a certain amount of the supported catalyst 24.

Finally, the upgraded feedstock 20 withdrawn from the ebullated bedreactor 10 is introduced into a hot separator 42. In the case where thefeedstock 14 contains a significant quantity of asphaltenes (e.g., about10% or more), the hot separator 42 may need to be operated at asubstantially cooler temperature than the hydrocracking temperaturewithin the ebullated bed reactor 10 in order to reduce the tendency ofasphaltene free radicals to form and foul the hot separator 42 anddownstream apparatus. In such cases, quench oil 44 is added to cool theupgraded feedstock 20. The hot separator 42 separates the volatilefraction 46, which is withdrawn from the top of hot separator 42, fromthe non-volatile fraction 48, which is withdrawn from the bottom of hotseparator 42. It will be appreciated that adding the quench oil 44reduces the ratio of the volatile fraction 46 to the non-volatilefraction 48, thereby reducing the efficiency of the hot separationprocess.

FIG. 2B schematically depicts an ebullated bed reactor 110 used in theH-Oil hydrocracking system developed by Hydrocarbon ResearchIncorporated, presently operated by Husky Oil in Alberta, Canada, whichis an example of an ebullated bed hydroprocessing system that can beupgraded according to the invention. Ebullated bed reactor 110 includesan input port 112 through which a heavy oil feedstock 114 andpressurized hydrogen gas 116 are introduced and an output port 118through which upgraded feedstock 120 is withdrawn. An expanded catalystzone 122 comprising a porous supported catalyst 124 is bounded by adistributor grid plate 126, which separates the expanded catalyst zone122 from a lower catalyst free zone 128 between the bottom of thereactor 110 and the distributor grid plate 126, and an upper end 129,which defines an approximate boundary between the expanded catalyst zone122 and an upper catalyst free zone 130. A boundary 131 shows theapproximate level of supported catalyst 124 when not in an expanded orfluidized state.

Feedstock is continuously recirculated within the reactor 110 by meansof a recycling channel 132 in communication with an ebullating pump 134disposed outside of the reactor 110. Feedstock is drawn through afunnel-shaped recycle cup 136 from the upper catalyst free zone 130. Therecycle cup 136 is spiral-shaped, which helps separate hydrogen bubbles125 from the feedstock 136 so as to prevent cavitation of the ebullatingpump 134. Recycled feedstock enters the lower catalyst free zone 128,where it is blended with the feedstock 116 and hydrogen gas 118, and themixture passes up through the distributor grid plate 126 and into theexpanded catalyst zone 122. Fresh catalyst 124 is introduced into theexpanded catalyst zone 122 through a catalyst input tube 136, and spentcatalyst 124 is withdrawn from the expanded catalyst zone 122 through acatalyst discharge tube 140.

The main difference between the H-Oil ebullated bed reactor 110 and theLC-Fining ebullated bed reactor 10 is the location of the ebullatingpump. The ebullating pump 134 in the H-Oil reactor 110 is locatedexternal to the reaction chamber. The recirculating feedstock isintroduced through a recirculation port 141 at the bottom of the reactor110. The recirculation port 141 includes a bubble cap 143, which aids inevenly distributing the feedstock through the lower catalyst free zone128. The upgraded feedstock 120 is shown being sent to a hot separator142, which separates the volatile fraction 146 from the non-volatilefraction 148.

FIG. 2C schematically depicts a conventional ebullated bedhydroprocessing system 200 comprising multiple ebullated bed reactors.The hydroprocessing system 200, which is an LC-Fining hydroprocessingunit, includes three ebullated bed reactors 210 in series for upgradinga feedstock 214. The feedstock 214 is introduced into the firstebullated bed reactor 210 a together with hydrogen gas 216, both ofwhich are preliminary passed through respective heaters. The upgradedfeedstock 220 a from the first ebullated bed reactor 210 a is introducedtogether with additional hydrogen gas 216 into the second ebullated bedreactor 210 b. The upgraded feedstock 220 b from the second ebullatedbed reactor 210 b is introduced together with additional hydrogen gas216 into the third ebullated bed reactor 210 c.

The upgraded feedstock 220 c from the third ebullated bed reactor 210 cis sent to a high temperature separator 242 a, which separates thevolatile and non-volatile fractions. The volatile fraction 246 a thenpasses through a heat exchanger 250, which preheats hydrogen gas 216prior to being introduced into the first ebullated bed reactor 210 a.The somewhat cooled volatile fraction 246 a is sent to a mediumtemperature separator 242 b, which separates the remaining volatilefraction 246 b from a resulting liquid fraction 248 b that forms as aresult of cooling. The remaining volatile fraction 246 b is sentdownstream to a low temperature separator 246 c for further separationinto a gaseous fraction 252 c and a degassed liquid fraction 248 c.

The liquid fraction 248 a from the high temperature separator 242 a issent together with the resulting liquid fraction 248 b from the mediumtemperature separator 242 b to a low pressure separator 242 d, whichseparates hydrogen rich gas 252 d from a degassed liquid fraction 248 d,which is then mixed with the degassed liquid fraction 248 c from the lowtemperature separator 242 c and fractionated into products. The gaseousfraction 252 c from the low temperature separator 242 c is purified intooff gas, purge gas, and hydrogen gas 216. The hydrogen gas 216 iscompressed, mixed with make-up hydrogen gas 216 a, and either passedthrough heat exchanger 250 and introduced into the first ebullated bedreactor 210 a together with the feedstock 216 or introduced directlyinto second and third ebullated bed reactors 210 b and 210 b.

B. Preparation and Characteristics of Colloidal or Molecular Catalyst

The inventive methods and systems for upgrading a heavy oil feedstockinclude the preliminary step of, or sub-system for, preparing a heavyoil feedstock so as to have a colloidal or molecular catalyst dispersedtherein, an example of which is schematically illustrated in the flowdiagram depicted in FIG. 3. According to one embodiment, an oil solublecatalyst precursor composition is pre-mixed with a diluent hydrocarbonstream to form a diluted precursor mixture. Preparing a heavy oilfeedstock to include a colloidal or molecular catalyst also forms partof exemplary methods for upgrading a pre-existing ebullated bedhydroprocessing system, as discussed more fully below.

The oil soluble catalyst precursor preferably has a decompositiontemperature in a range from about 100° C. (212° F.) to about 350° C.(662° F.), more preferably in a range of about 150° C. (302° F.) toabout 300° C. (572° F.), and most preferably in a range of about 175° C.(347° F.) to about 250° C. (482° F.). Examples of exemplary catalystprecursor compositions include organometallic complexes or compounds,more specifically, oil soluble compounds or complexes of transitionmetals and organic acids. A currently preferred catalyst precursor ismolybdenum 2-ethylhexanoate (also commonly known as molybdenum octoate)containing 15% by weight molybdenum and having a decompositiontemperature or range high enough to avoid substantial decomposition whenmixed with a heavy oil feedstock at a temperature below about 250° C.(482° F.). Other exemplary precursor compositions include, but are notlimited to, molybdenum naphthanate, vanadium naphthanate, vanadiumoctoate, molybdenum hexacarbonyl, vanadium hexacarbonyl, and ironpentacarbonyl. One of skill in the art can, following the presentdisclosure, select a mixing temperature profile that results in intimatemixing of a selected precursor composition without substantialdecomposition prior to formation of the colloidal or molecular catalyst.

Examples of suitable hydrocarbon diluents include, but are not limitedto, vacuum gas oil (which typically has a boiling range of 360-524° C.)(680-975° F.), decant oil or cycled oil (which typically has a boilingrange of 360°-550° C.) (680-1022° F.), and light gas oil (whichtypically has a boiling range of 200°-360° C.) (392-680° F.).

The ratio of catalyst precursor composition to hydrocarbon oil diluentis preferably in a range of about 1:500 to about 1:1, more preferably ina range of about 1:150 to about 1:2, and most preferably in a range ofabout 1:100 to about 1:5 (e.g., 1:100, 1:50, 1:30, or 1:10).

The catalyst precursor composition is advantageously mixed with thehydrocarbon diluent at a temperature below which a significant portionof the catalyst precursor composition starts to decompose, preferably,at temperature in a range of about 25° C. (77° F.) to about 250° C.(482° F.), more preferably in range of about 50° C. (122° F.) to about200° C. (392° F.), and most preferably in a range of about 75° C. (167°F.) to about 150° C. (302° F.), to form the diluted precursor mixture.It will be appreciated that the actual temperature at which the dilutedprecursor mixture is formed typically depends largely on thedecomposition temperature of the particular precursor composition thatis utilized. The precursor composition is preferably mixed with thehydrocarbon oil diluent for a time period in a range of about 1 secondto about 20 minutes, more preferably in a range of about 5 seconds toabout 10 minutes, and most preferably in a range of about 20 seconds toabout 5 minutes. The actual mixing time is dependent, at least in part,on the temperature (i.e., which affects the viscosity of the fluids) andmixing intensity. Mixing intensity is dependent, at least in part, onthe number of stages e.g., for in-line static mixer.

Whereas it is within the scope of the invention to directly blend thecatalyst precursor composition with the heavy oil feedstock, care mustbe taken in such cases to mix the components for a time sufficient tothoroughly blend the precursor composition within the feedstock beforesubstantial decomposition of the precursor composition has occurred. Forexample, U.S. Pat. No. 5,578,197 to Cyr et al., the disclosure of whichis incorporated by reference, describes a method whereby molybdenum2-ethyl hexanoate was mixed with bitumen vacuum tower residuum for 24hours before the resulting mixture was heated in a reaction vessel toform the catalyst compound and to effect hydrocracking (see col. 10,lines 4-43). Whereas 24-hour mixing in a testing environment may beentirely acceptable, such long mixing times may make certain industrialoperations prohibitively expensive.

It has now been found that preblending the precursor composition with ahydrocarbon diluent prior to blending the diluted precursor mixture withthe heavy oil feedstock greatly aids in thoroughly and intimatelyblending the precursor composition within the feedstock, particularly inthe relatively short period of time required for large-scale industrialoperations to be economically viable. Forming a diluted precursormixture shortens the overall mixing time by (1) reducing or eliminatingdifferences in solubility between the more polar catalyst precursorcomposition and the heavy oil feedstock, (2) reducing or eliminatingdifferences in rheology between the catalyst precursor composition andthe heavy oil feedstock, and/or (3) breaking up the catalyst precursormolecules to form a solute within a hydrocarbon oil diluent that is muchmore easily dispersed within the heavy oil feedstock. It is particularlyadvantageous to first form a diluted precursor mixture in the case wherethe heavy oil feedstock contains water (e.g., condensed water).Otherwise, the greater affinity of the water for the polar catalystprecursor composition can cause localized agglomeration of the precursorcomposition, resulting in poor dispersion and formation of micron-sizedor larger catalyst particles. The hydrocarbon oil diluent is preferablysubstantially water free (i.e., contains less than about 0.5% water) toprevent the formation of substantial quantities of micron-sized orlarger catalyst particles.

The diluted precursor mixture is then combined with the heavy oilfeedstock and mixed for a time sufficient and in a manner so as todisperse the catalyst precursor composition throughout the feedstock inorder to yield a conditioned feedstock composition in which theprecursor composition is thoroughly mixed within the heavy oilfeedstock. In order to obtain sufficient mixing of the catalystprecursor composition within the heavy oil feedstock so as to yield acolloidal or molecular catalyst upon decomposition of the precursorcomposition, the diluted precursor mixture and heavy oil feedstock arepreferably mixed for a time period in a range of about 1 second to about20 minutes, more preferably in a range from about 5 second to about 10minutes, and most preferably in a range of about 20 seconds to about 3minutes. Increasing the vigorousness and/or shearing energy of themixing process generally reduce the time required to effect thoroughmixing.

Examples of mixing apparatus that can be used to effect thorough mixingof the catalyst precursor composition and heavy oil feedstock include,but are not limited to, high shear mixing such as mixing created in avessel with a propeller or turbine impeller; multiple static in-linemixers; multiple static in-line mixers in combination with in-line highshear mixers; multiple static in-line mixers in combination with in-linehigh shear mixers; multiple static in-line mixers in combination within-line high shear mixers follows by a pump around in the surge vessel;combinations of the above followed by one or more multi-stagecentrifugal pumps; and one or more multi-stage centrifugal pumps.According to one embodiment, continuous rather than batch-wise mixingcan be carried out using high energy pumps having multiple chamberswithin which the catalyst precursor composition and heavy oil feedstockare churned and mixed as part of the pumping process itself. Theforegoing mixing apparatus may also be used for the pre-mixing processdiscussed above in which the catalyst precursor composition is mixedwith the hydrocarbon oil diluent to form the catalyst precursor mixture.

Alternatively, the diluted precursor mixture can be initially mixed with20% of the heavy oil feedstock, the resulting mixed heavy oil feedstockcan be mixed in with another 40% of the heavy oil feedstock, and theresulting 60% of the mixed heavy oil feedstock can be mixed in with theremainder 40% of heavy oil in accordance with good engineering practiceof progressive dilution to thoroughly dispersed the catalyst precursorin the heavy oil feedstock. Vigorous adherence to the mixing time in theappropriate mixing devices or methods described herein should still beused in the progressive dilution approach.

In the case of heavy oil feedstocks that are solid or extremely viscousat room temperature, such feedstocks may advantageously be heated inorder to soften them and create a feedstock having sufficiently lowviscosity so as to allow good mixing of the oil soluble catalystprecursor into the feedstock composition. In general, decreasing theviscosity of the heavy oil feedstock will reduce the time required toeffect thorough and intimate mixing of the oil soluble precursorcomposition within the feedstock. However, the feedstock should not beheated to a temperature above which significant decomposition of thecatalyst precursor composition occurs until after thorough and completemixing to form the blended feedstock composition. Prematurelydecomposing the catalyst precursor composition generally results in theformation of micron-sized or larger catalyst particles rather than acolloidal or molecular catalyst. The heavy oil feedstock and dilutedprecursor mixture are preferably mixed and conditioned at a temperaturein a range of about 25° C. (77° F.) to about 350° C. (662° F.), morepreferably in a range of about 50° C. (122° F.) to about 300° C. (572°F.), and most preferably in a range of about 75° C. (167° F.) to about250° C. (482° F.) to yield the conditioned feedstock.

After the catalyst precursor composition has been well-mixed throughoutthe heavy oil feedstock so as to yield the conditioned feedstockcomposition, this composition is then heated to above the temperaturewhere significant decomposition of the catalyst precursor compositionoccurs in order to liberate the catalyst metal therefrom so as to formthe final active catalyst. According to one embodiment, the metal fromthe precursor composition is believed to first form a metal oxide, whichthen reacts with sulfur liberated from the heavy oil feedstock to yielda metal sulfide compound that is the final active catalyst. In the casewhere the heavy oil feedstock includes sufficient or excess sulfur, thefinal activated catalyst may be formed in situ by heating the heavy oilfeedstock to a temperature sufficient to liberate the sulfur therefrom.In some cases, sulfur may be liberated at the same temperature that theprecursor composition decomposes. In other cases, further heating to ahigher temperature may be required.

If the oil soluble catalyst precursor composition is thoroughly mixedthroughout the heavy oil feedstock, at least a substantial portion ofthe liberated metal ions will be sufficiently sheltered or shielded fromother metal ions so that they can form a molecularly-dispersed catalystupon reacting with sulfur to form the metal sulfide compound. Under somecircumstances, minor agglomeration may occur, yielding colloidal-sizedcatalyst particles. However, it is believed that taking care tothoroughly mix the precursor composition throughout the feedstock willyield individual catalyst molecules rather than colloidal particles.Simply blending, while failing to sufficiently mix, the catalystprecursor composition with the feedstock typically causes formation oflarge agglomerated metal sulfide compounds that are micron-sized orlarger.

In order to form the metal sulfide catalyst, the blended feedstockcomposition is preferably heated to a temperature in a range of about275° C. (527° F.) to about 450° C. (842° F.), more preferably in a rangeof about 350° C. (662° F.) to about 440° C. (824° F.), and mostpreferably in a range of about 375° C. (707° F.) to about 420° C. (788°F.). According to one embodiment, the conditioned feedstock is heated toa temperature that is about 100° C. (180° F.) less than thehydrocracking temperature within the hydrocracking reactor, preferablyabout 50° C. (90° F.) less than the hydrocracking temperature. Accordingto one embodiment, the colloidal or molecular catalyst is formed duringpreheating before the heavy oil feedstock is introduced into thehydrocracking reactor. According to another embodiment, at least aportion of the colloidal or molecular catalyst is formed in situ withinthe hydrocracking reactor itself. In some cases, the colloidal ormolecular catalyst can be formed as the heavy oil feedstock is heated toa hydrocracking temperature prior to or after the heavy oil feedstock isintroduced into a hydrocracking reactor. The initial concentration ofthe catalyst metal in the colloidal or molecular catalyst is preferablyin a range of about 5 ppm to about 500 ppm by weight of the heavy oilfeedstock, more preferably in a range of about 15 ppm to about 300 ppm,and most preferably in a range of about 25 ppm to about 175 ppm. Thecatalyst may become more concentrated as volatile fractions are removedfrom a non-volatile resid fraction.

In the case where the heavy oil feedstock includes a significantquantity of asphaltene molecules, the catalyst molecules or colloidalparticles will preferentially associate with, or remain in closeproximity to, the asphaltene molecules. Asphaltene has a greateraffinity for the colloidal or molecular catalyst since asphaltenemolecules are generally more hydrophilic and less hydrophobic than otherhydrocarbons contained within the heavy oil feedstock. Because thecolloidal or molecular catalyst tends to be very hydrophilic, theindividual particles or molecules will tend to migrate toward the morehydrophilic moieties or molecules within the heavy oil feedstock. FIG. 4schematically depicts catalyst molecules, or colloidal particles “X”associated with, or in close proximity to, the asphaltene molecules.

While the highly polar nature of the catalyst compound causes or allowsthe colloidal or the molecular catalyst to associate with asphaltenemolecules, it is the general incompatibility between the highly polarcatalyst compound and the hydrophobic heavy oil feedstock thatnecessitates the aforementioned intimate or thorough mixing of the oilsoluble catalyst precursor composition within the heavy oil feedstockprior to decomposition of the precursor and formation of the colloidalor molecular catalyst. Because metal catalyst compounds are highlypolar, they cannot be effectively dispersed within a heavy oil feedstockin colloidal or molecular form if added directly thereto or as part ofan aqueous solution or an oil and water emulsion. Such methodsinevitably yield micron-sized or larger catalyst particles.

Reference is now made to FIGS. 5A and 5B, which schematically depict ananometer-sized molybdenum disulfide crystal. FIG. 5A is a top view, andFIG. 5B is a side view of a molybdenum disulfide crystal. Molecules ofmolybdenum disulfide typically form flat, hexagonal crystals in whichsingle layers of molybdenum (Mo) atoms are sandwiched between layers ofsulfur (S) atoms. The only active sites for catalysis are on the crystaledges where the molybdenum atoms are exposed. Smaller crystals have ahigher percentage of molybdenum atoms exposed at the edges.

The diameter of a molybdenum atom is approximately 0.3 nm, and thediameter of a sulfur atom is approximately 0.2 nm. A nanometer-sizedcrystal of molybdenum disulfide has 7 molybdenum atoms sandwiched inbetween 14 sulfur atoms. As best seen in FIG. 5A, 6 out of 7 (85.7%) ofthe total molybdenum atoms will be exposed at the edge and available forcatalytic activity. In contrast, a micron-sized crystal of molybdenumdisulfide has several million atoms, with only about 0.2% of the totalmolybdenum atoms being exposed at the crystal edge and available forcatalytic activity. The remaining 99.8% of the molybdenum atoms in themicron-sized crystal are embedded within the crystal interior and aretherefore unavailable for catalysis. This means that nanometer-sizedmolybdenum disulfide particles are, at least in theory, orders ofmagnitude more efficient than micron-sized particles in providing activecatalyst sites.

In practical terms, forming smaller catalyst particles results in morecatalyst particles and more evenly distributed catalyst sites throughoutthe feedstock. Simple mathematics dictates that forming nanometer-sizedparticles instead of micron-sized particles will result in approximately1000³ (or 1 million) to 100³ (or 1 billion) times more particlesdepending on the size and shape of the catalyst crystals. That meansthere are approximately 1 million to 1 billion times more points orlocations within the feedstock where active catalyst sites reside.Moreover, nanometer-sized or smaller molybdenum disulfide particles arebelieved to become intimately associated with asphaltene molecules, asshown in FIG. 4. In contrast, micron-sized or larger catalyst particlesare believed to be far too large to become intimately associated with orwithin asphaltene molecules.

C. Ebullated Bed Reactors and Systems that Employ the Colloidal orMolecular Catalyst

FIG. 6 schematically illustrates an exemplary ebullated bedhydroprocessing system 400 according to the invention. Ebullated bedhydroprocessing system 400 includes a slurry phase hydrocracking reactor402, a hot separator 404, and an ebullated bed reactor 430 disposedbetween the slurry phase reactor 402 and the hot separator 404. A heavyoil feedstock 406 is initially blended and conditioned with a catalystprecursor composition 408 within a mixer 410, preferably after firstpre-mixing the precursor composition 408 with a diluent as discussedabove. The conditioned feedstock from the mixer 410 is pressurized by apump 412, passed through a pre-heater 413, and continuously orperiodically fed into the slurry phase reactor 402 together withhydrogen gas 414 through an input port 418 located at or near the bottomof the slurry phase reactor 402. A stirrer 420 at the bottom of theslurry phase reactor 402 helps to more evenly disperse the hydrogen 414,schematically depicted as gas bubbles 422, within the feedstock 406.Alternatively or in addition to the stirrer 420, the slurry phasereactor 402 may include a recycle channel, recycling pump, anddistributor grid plate (not shown) as in conventional ebullated bedreactors to promote more even dispersion of reactants, catalyst, andheat. The colloidal or molecular catalyst within the feedstock 406 isschematically depicted as catalyst particles 424. It will be appreciatedthat gas bubbles 422 and catalyst particles 424 are shown oversized sothat they may be seen in the drawing. In reality, they are likelyinvisible to the naked eye.

The heavy oil feedstock 406 is catalytically upgraded in the presence ofthe hydrogen and colloidal or molecular catalyst within the slurry phasereactor 402 to form an upgraded feedstock 426, which is continuouslywithdrawn along with residual hydrogen and from the slurry phase reactor402 through an output port 428 located at or near the top of the slurryphase reactor 402. The upgraded feedstock 426 is optionally pressurizedby pump 432 and introduced together with supplemental hydrogen 434 intothe ebullated bed reactor 430 through an input port 436 located at ornear the bottom of the ebullated bed reactor 430. The upgraded feedstock426 contains residual or molecular catalyst, schematically depicted ascatalyst particles 424′ within the ebullated bed reactor 430, andhydrogen. The ebullated bed reactor 430 also includes an output port 438at or near the top of the ebullated bed reactor 430 through which afurther hydroprocessed feedstock 440 is withdrawn.

The ebullated bed reactor 430 further includes an expanded catalyst zone442 comprising a porous supported catalyst 444. A lower supportedcatalyst free zone 448 is located below the expanded catalyst zone 442,and above the expanded catalyst zone 442 is an upper supported catalystfree zone 450. Residual colloidal or molecular catalyst 424′ isdispersed throughout the feedstock within the ebullated bed reactor 430,including both the expanded catalyst zone 442 and the supported catalystfree zones 448, 450, 452 thereby being available to promote upgradingreactions within what constitute catalyst free zones in conventionalebullated bed reactors. Feedstock within the ebullated bed reactor 430is continuously recirculated from the upper supported catalyst free zone450 to the lower supported catalyst free zone 448 by means of arecycling channel 452 in communication with an ebullating pump 454. Atthe top of the recycling channel 452 is a funnel-shaped recycle cup 456through which feedstock is drawn from the upper supported catalyst freezone 450. The recycled feedstock is blended with fresh upgradedfeedstock 426 and supplemental hydrogen gas 434.

Fresh supported catalyst 444 is introduced into the ebullated bedreactor 430 reactor through a catalyst input tube 458, and spentsupported catalyst 444 is withdrawn through a catalyst withdrawal tube460. Whereas the catalyst withdrawal tube 460 is unable to differentiatebetween fully spent catalyst, partially spent but active catalyst, andfresh catalyst, the existence of residual colloidal or moleculecatalyst, schematically shown as catalyst particles 424′ within theebullated bed reactor 430, provides additional catalytic hydrogenationactivity, both within the expanded catalyst zone 442, the recyclechannel 452, and the lower and upper supported catalyst free zones 448,450. Capping of free radicals outside of the supported catalyst 444minimizes formation of sediment and coke precursors, which are oftenresponsible for deactivating the supported catalyst. This has the effectof reducing the amount of supported catalyst 444 that would otherwise berequired to carry out a desired hydroprocessing reaction. It alsoreduces the rate at which the supported catalyst 444 must be withdrawand replenished.

Finally, the further hydroprocessed feedstock 440 withdrawn from theebullated bed reactor 430 is introduced into the hot separator 404. Thehot separator 404 separates the volatile fraction 405, which iswithdrawn from the top of hot separator 404, from the non-volatilefraction 407, which is withdrawn from the bottom of hot separator 404.According to one embodiment, the hot separator is advantageouslyoperated at a temperature within about 20° F. (about 11° C.) of thehydroprocessing temperature within the ebullated bed reactor 430. Thenon-volatile fraction 407 still contains residual colloidal or molecularcatalyst, schematically depicted as catalyst particles 424″, andresidual hydrogen gas, schematically depicted as bubbles 422″, dispersedtherein. As a result, beneficial hydrogenation reactions betweenhydrocarbon free radicals that still exist and/or that are formed withinthe non-volatile fraction 407 and the residual hydrogen 422″ can becatalyzed by the residual colloidal or molecular catalyst 424″ withinthe hot separator 404. There is therefore no need to add quenching oilto the further hydroprocessed feedstock 440 to prevent fouling of thehot separator 404.

FIGS. 7A-7C further illustrate exemplary ebullated bed hydroprocessingsystems according to the invention, including upgraded systems frompre-existing ebullated bed systems. FIG. 7A is a box diagram thatschematically illustrates an exemplary hydroprocessing system 500 whichincludes an ebullated bed reactor 502 and that differs from aconventional ebullated bed system by blending a catalyst precursorcomposition 504 with a heavy oil feedstock 506 prior to introducing thefeedstock 506 into the ebullated bed reactor 502 and downstreamapparatus 508. Downstream apparatus 508 may comprise one or moreadditional ebullated bed reactors, other hydrocracking orhydroprocessing reactors, hot separators, distillation towers, a guardbed, and the like.

The heavy oil feedstock 506 may comprise any desired fossil fuelfeedstock and/or fraction thereof including, but not limited to, one ormore of heavy crude, oil sands bitumen, bottom of the barrel fractionsfrom crude oil, atmospheric tower bottoms, vacuum tower bottoms, coaltar, liquefied coal, and other resid fractions. According to oneembodiment, the heavy oil feedstock 506 includes a significant fractionof high boiling point hydrocarbons (i.e., at or above 343° C. (650° F.),more particularly at or above about 524° C. (975° F.)) and/orasphaltenes. Asphaltenes are complex hydrocarbon molecules that includea relatively low ratio of hydrogen to carbon that is the result of asubstantial number of condensed aromatic and naphthenic rings withparaffinic side chains (See FIG. 1). Sheets consisting of the condensedaromatic and naphthenic rings are held together by heteroatoms such assulfur or nitrogen and/or polymethylene bridges, thio-ether bonds, andvanadium and nickel complexes. The asphaltene fraction also contains ahigher content of sulfur and nitrogen than does crude oil or the rest ofthe vacuum resid, and it also contains higher concentrations ofcarbon-forming compounds (i.e., that form coke precursors and sediment).

The catalyst precursor composition 504 is intimately mixed with thefeedstock 506 prior to introducing the feedstock into the ebullated bedreactor 502. According to one embodiment, the catalyst precursorcomposition may be pre-mixed with a diluent hydrocarbon stream (notshown) to form a diluted precursor mixture that is then mixed with theheavy oil feedstock 506. The colloidal or molecular catalyst may begenerated prior to introducing the feedstock 506 into the ebullated bedreactor 502 and/or generated in situ within the ebullated bed reactor502. In this way, the ebullated bed reactor 502 within hydroprocessingsystem 500 employs a colloidal or molecular catalyst, which provides thebenefits described above (e.g., promotes beneficial upgrading reactionsinvolving asphaltenes or other large hydrocarbon molecules that are toolarge to diffuse into the pores of a porous supported catalyst andprovides a hydroprocessing catalyst in what would otherwise constitutecatalyst free zones inherent in an ebullated bed reactor and downstreamapparatus 508).

FIG. 7B is a box diagram that schematically illustrates an exemplaryebullated bed hydroprocessing system 600 that includes a slurry phasereactor 610 upstream from an ebullated bed reactor 602 and downstreamapparatus 608. The slurry phase reactor 610 may comprise a previouslyoperating ebullated bed reactor that has been converted into a slurryphase reactor, or it may comprise a newly constructed reactor within thehydroprocessing system 600. The catalyst precursor composition 604 isintimately mixed with the heavy oil feedstock 606 prior to introducingthe feedstock 606 into the slurry phase reactor 610. The slurry phasereactor 610 yields an upgraded feedstock, which is thereafter introducedinto the ebullated bed reactor 602, either directly or after additionalprocessing (e.g., one or more additional slurry phase reactors, one ormore hot separators, and/or one or more ebullated bed reactors upstreamfrom ebullated bed reactor 602). The hydroprocessing system 600 mayfurther include downstream apparatus 608 as desired to complete thesystem (e.g., one or more of a guard bed, fixed bed hydrotreatingreactor, hot separator, and the like).

FIG. 7C is a box diagram that schematically illustrates an exemplaryebullated bed hydroprocessing system 700 that includes a slurry phasereactor 710 upstream from an ebullated bed reactor 702 and a guard bed712 downstream from the ebullated bed reactor 702. The catalystprecursor composition 704 is intimately mixed with the heavy oilfeedstock 706 prior to introducing the feedstock 706 into the slurryphase reactor 710. The slurry phase reactor 710 yields an upgradedfeedstock, which is thereafter introduced into the ebullated bed reactor702 for further hydrocracking and/or hydrotreating. The further upgradedmaterial from the ebullated bed reactor 702 is sent to the guard bed712, which advantageously comprises a fixed bed reactor that includes acatalyst that is specially designed to remove targeted impurities (e.g.one or more of metal impurities such as nickel and vanadium and at leasta portion of the colloidal or molecular catalyst). The hydroprocessingsystem 700 may further include downstream apparatus 708 as desired tocomplete the system.

Any of the foregoing exemplary ebullated bed hydroprocessing systems, aswell as others, that may be made by those of skill in the art based onthe teachings disclosed herein, may comprise entirely new equipment(e.g., a “green field operation”), or they may integrate one or morecomponents from pre-existing hydroprocessing systems. It is within thescope of the invention to upgrade a pre-existing ebullated bed reactoror hydroprocessing system to yield a hydroprocessing system according tothe invention.

D. Methods for Upgrading an Existing Ebullated Bed Reactor or System

FIGS. 8A-8D show box diagrams that schematically illustrate exemplarymethods for upgrading pre-existing ebullated bed reactors and systemsaccording to the invention. FIG. 8A is a box diagram of an exemplarymethod 800 for upgrading a pre-existing ebullated bed reactor. The firststep or act involves operating a pre-existing ebullated bed reactorusing a porous supported ebullated bed catalyst. Such catalyststypically have a size of, for example, ¼″×⅛″ or ¼″× 1/16″ (6.35 mm×3.175mm or 6.35 mm×1.5875 mm), and include a porous inert support materialand active metal catalyst sites disposed within the pores of the supportmaterial. As discussed above, the heavy oil feedstock molecules, moreparticularly the hydrocarbon free radicals generated by thermalcracking, must diffuse into the pores of the catalyst. As a result,larger molecules such as asphaltenes that are too large to enter thepores cannot be effectively hydroprocessed using the porous supportedcatalyst. Moreover, hydrocarbon free radicals of any size within thecatalyst free zones of the ebullated bed reactor cannot behydroprocessed because they are not in contact with the porous supportedcatalyst, nor can molecules outside the pores of the porous supportedcatalyst.

According to one embodiment of the invention, the ebullated bed reactoris initially upgraded by operating the reactor using a colloidal ormolecular catalyst in addition to the porous supported catalyst. Thecolloidal or molecular catalyst can be generated within a heavy oilfeedstock prior to introducing the feedstock into the ebullated bedreactor, or the feedstock may contain a well-dispersed catalystprecursor composition that forms the colloidal or molecular catalyst insitu within the ebullated bed reactor. Exemplary methods for preparingthe colloidal or molecular catalyst within a feedstock are describedmore fully above.

Operating the ebullated bed reactor using the colloidal or molecularcatalyst immediately helps to offset at least two deficiencies inherentin the ebullated bed reactor prior to upgrading according to theinvention. First, the colloidal or molecular catalyst will remain withinthe heavy oil feedstock as it passes into what were previous thecatalyst free zones of the ebullated bed reactor. As a result, thecolloidal or molecular catalyst allows beneficial upgrading reactions ofthe feedstock throughout the entire reaction chamber, including whatprevious constituted catalyst free zones (e.g., hydrocarbon freeradicals formed anywhere in the reaction chamber as a result of thermalcracking can be hydroprocessed and capped with hydrogen anywhere in thereaction chamber, as well as within downstream processing equipment,such as hot separators. Second, asphaltenes and other hydrocarbonmolecules that are too large to enter the pores of the supportedcatalyst can be hydroprocessed by the colloidal or molecular catalyst,both within the expanded catalyst zone and what previously constitutedthe catalyst free zones prior to upgrading. The result is increasedconversion of the feedstock and decreased fouling of the equipment.

Either before, but typically after, beginning to operate the ebullatedbed reactor using the colloidal or molecular catalyst, the concentrationof porous supported catalyst within the ebullated bed reactor can beadjusted to a desired level. In some cases it may be desirable to simplymaintain the concentration of supported catalyst at the same level asbefore upgrading the ebullated bed reactor and operating the reactor ata higher conversion or using a lower quality feedstock. However, becausethe catalytic effect of the colloidal or molecular catalyst is additiveto that of the supported catalyst, it may be possible in many cases toreduce the concentration of the porous supported catalyst. Theconcentration of the supported catalyst can be reduced from an initiallevel to a reduced level all at once, or it may be done gradually insteps. In some cases it may be possible or desirable to eliminate thesupported catalyst entirely, which would convert the ebullated bedreactor into a slurry phase reactor.

It is also within the scope of the invention to vary the concentrationof the supported catalyst and/or the colloidal or molecular catalyst inorder to optimize the hydroprocessing of different feedstocks of varyingquality. In this way the precise ratio of supported catalyst andcolloidal or molecular catalyst can be fined-tuned to a particular heavyoil feedstock. For example, for feedstocks that include relatively highconcentrations of asphaltenes, it may be advantageous to increase theratio of colloidal or molecular catalyst to supported catalyst.Conversely, for feedstocks that include a relatively low concentrationof asphaltenes, it may be advantageous to decrease the ratio ofcolloidal or molecular catalyst to supported catalyst.

FIG. 8B is a box diagram of an exemplary method 802 for upgrading apre-existing ebullated bed hydroprocessing system comprising multipleebullated bed reactors. It should be understood that operating andupgrading an ebullated bed hydroprocessing system comprising multipleebullated bed reactors as illustrated in FIG. 8B is not mutuallyexclusive to operating and upgrading an ebullated bed reactor asillustrated in FIG. 8A. The first step or act involves operating apre-existing ebullated bed hydroprocessing system comprising multipleebullated bed reactors using a porous supported catalyst within eachreactor.

According to one embodiment of the invention, the ebullated bedhydroprocessing system is initially upgraded by operating one or more ofthe ebullated bed reactors using a colloidal or molecular catalyst inaddition to the porous supported catalyst. Operating one or moreebullated bed reactors using the colloidal or molecular catalyst allowsbeneficial upgrading reactions of the feedstock throughout the entirereaction chamber of the one or more ebullated bed reactors, includingwhat previous constituted catalyst free zones, and allows forhydroprocessing of asphaltenes and other hydrocarbon molecules too largeto enter the pores of the supported catalyst. The result is increasedconversion of the feedstock and decreased fouling of the system.

Either before or after beginning to operate one or more ebullated bedreactors using the colloidal or molecular catalyst, the concentration ofporous supported catalyst within one or more ebullated bed reactors canbe adjusted to a desired level. The concentration of supported catalystin all the ebullated bed reactors can be maintained at their initiallevels or they may all be adjusted to a desired lower level, eithersimultaneously or sequentially. Alternatively, the concentration of thesupported catalyst and/or the colloidal or molecular catalyst can bevaried from reactor to reactor to account for differences in the qualityof feedstock that is introduced into each ebullated bed reactor. Itwithin the scope of the invention to eliminate the supported catalystentirely within one or more ebullated bed reactors, while keeping atleast some of the supported catalyst within on or more other ebullatedbed reactors. According to one embodiment, the last ebullated bedreactor in a series may include a porous catalyst designed to remove atleast a portion of the colloidal or molecular catalyst from the upgradedfeedstock. According to one embodiment, supplemental colloidal ormolecular catalyst can be added to the upgraded feedstock and/or thedownstream reactor(s) to offset possible catalyst removal by the poroussupported catalyst in the upstream reactor(s).

FIG. 8C is a box diagram of an exemplary method 804 for upgrading apre-existing ebullated bed hydroprocessing system comprising at leastone ebullated bed reactor. It should be understood that operating andupgrading at least one ebullated bed reactor as illustrated in FIG. 8Cis not mutually exclusive to operating and upgrading an ebullated bedreactor as illustrated in FIG. 8A or operating and upgrading ahydroprocessing system comprising multiple ebullated bed reactors asillustrated in FIG. 8B. The first step or act involves operating apre-existing ebullated bed hydroprocessing system comprising at leastone ebullated bed reactor using a porous supported catalyst.

According to one embodiment of the invention, the ebullated bedhydroprocessing system is initially upgraded by beginning operating oneor more slurry phase reactors upstream from at least one ebullated bedreactor using a colloidal or molecular catalyst within the slurry phasereactor. Operating one or more slurry phase reactors using the colloidalor molecular catalyst allows beneficial upgrading reactions of thefeedstock prior to introducing the upgraded feedstock into the at leastone ebullated bed reactor. Because of this, the upgraded feedstockintroduced into the ebullated bed reactor will be of higher qualitycompared to the quality of the feedstock prior to upgrading. Forexample, the upgraded feedstock from the slurry phase reactor has alower average boiling point and contains fewer asphaltenes and otherlarger molecules that might otherwise tend to foul the at least oneebullated bed reactor.

In addition, the upgraded feedstock from the slurry phase reactor thatis introduced into the ebullated bed reactor(s) contains the colloidalor molecular catalyst, which will further improve the hydroprocessingreaction in the ebullated bed reactor for the reasons given above. Asabove, it is within the scope of the invention to maintain the initialconcentration of supported catalyst. Alternatively, the concentration ofthe supported catalyst may be reduced or altered depending on thequality of the feedstock or a desired conversion.

In a variation of the method illustrated in FIG. 8C, a guard bed may beadded after the last ebullated bed in order to remove the molecular orcolloidal catalyst and/or other metals that may remain in thehydroprocessed material produced by the upgraded ebullated bedhydroprocessing system. In addition to the guard bed, a fixed bedhydrotreating reactor may be installed after the guard bed.

FIG. 8D is a box diagram of an exemplary method 806 for upgrading apre-existing ebullated bed hydroprocessing system comprising at leastone ebullated bed reactor in a manner that is expressly designed toprolong the life of the supported catalyst within the ebullated bed. Itshould be understood that operating and upgrading at least one ebullatedbed reactor as illustrated in FIG. 8D is not mutually exclusive tooperating and upgrading an ebullated bed reactor as illustrated in FIG.8A, a hydroprocessing system comprising multiple ebullated bed reactorsas illustrated in FIG. 8B, or at least one ebullated reactor as inillustrated in FIG. 8C. The first step or act involves operating apre-existing ebullated bed hydroprocessing system comprising at leastone ebullated bed reactor using a porous supported catalyst.

As in the immediately preceding example, the ebullated bedhydroprocessing system is initially upgraded by beginning operating oneor more slurry phase reactors upstream from the ebullated bed reactor(s)using a colloidal or molecular catalyst within the slurry phase reactor.After upgrading the feedstock in the one or more slurry phase reactors,and optionally one or more ebullated bed reactors upstream from theebullated bed reactor in question, the upgraded feedstock is processedso as to remove at least a portion of the colloidal or molecularcatalyst, as well as any metal impurities, prior to introducing thefeedstock into the ebullated bed reactor in question. This may beaccomplished, for example, by passing the upgraded feedstock through areactor that includes a porous catalyst that is designed to remove metalimpurities from a feedstock. The reactor containing the porous catalystfor removing metal impurities may be a fixed bed reactor (e.g., a guardbed) or it may be an ebullated bed containing the aforementionedcatalyst. The purified feedstock is then feed into and hydroprocessedusing the ebullated bed reactor in question.

The improved ebullated bed hydroprocessing methods and systems of thepresent invention preferably achieve conversion levels of at least about50%, more preferably at least about 65%, and most preferably at leastabout 80%. Use of the colloidal or molecular catalyst can achieveconversion levels up to about 95%. Moreover, whereas conventionalebullated bed systems typically have a lower conversion level for theasphaltene fraction as compared to the heavy oil feedstock as a whole,the improved ebullated bed hydroprocessing methods and systemspreferably maintain similar conversion levels for both the asphaltenefraction and the overall heavy oil feedstock.

III. Experimental Studies and Results

The following test studies demonstrate the effects and advantages ofusing a colloidal or molecular catalyst instead of, or in addition to, aconventional porous supported catalyst when hydroprocessing a heavy oilfeedstock that includes a significant quantity of asphaltenes.

Example 1

The ability of a colloidal or molecular catalyst and a porous supportedcatalyst to convert the asphaltene fraction of a heavy oil feedstock wascompared. A heavy oil feedstock comprising Cold Lake bitumen atmosphericresid and 300 ppm of a molybdenum disulfide catalyst in colloidal ormolecular form was introduced into a pilot slurry phase hydroprocessingreactor system and operated at various percent resid conversion levels.The pilot reactor system used in this test was similar to that shown inFIG. 10 (discussed more fully below), except that the pilot reactorsystem only had a single continuous flow slurry phase reactor having avolume of 1200 ml. The pilot reactor was a hollow tube and had nointernal liquid recycle system. The pilot plant experiments were carriedout under 2000 psig of hydrogen pressure, with a reaction temperatureover the range of 430-450° C. to control the conversion level and ahydrogen flow rate of 5000 standard cubic feet per barrel of heavy oil(SCF/bbl). The percent conversion of the asphaltenes versus the overallconversion level for the resid material when using the colloidal ormolecular catalyst is plotted in the chart shown at FIG. 9.

Cold Lake bitumen atmospheric resid was also hydroprocessed using aporous supported catalyst within a 3 phase, gas-liquid-solid continuousflow stirred reactor that was operated at various percent residconversion levels. The porous supported catalyst was contained within aspinning cage and experiments were carried out at 2000 psig hydrogenpressure at reaction temperature between 420-440° C. to control theconversion level. The percent conversion of the asphaltenes versus theoverall conversion level for the resid material when using the poroussupported catalyst is also plotted in the chart shown at FIG. 9.

According to the chart of FIG. 9, the comparative study showed that thepercent conversion of asphaltenes using the colloidal or molecularcatalyst was the same as the percent conversion of the resid material asa whole. That means the asphaltenes were converted into lower boilingmaterials at the same conversion level as the resid material as a whole,demonstrating that the colloidal or molecular catalyst was as active inconverting asphaltenes as other resid hydrocarbon molecules. Inpractical terms, the result is no incremental buildup of asphaltenes inthe feedstock.

In contrast, the percent conversion of asphaltenes using the poroussupported catalyst was half or less of the percent conversion of theresid fraction as a whole. That means the porous supported catalyst wassubstantially less effective in converting asphaltenes than otherhydrocarbons in the resid material, most likely because the largerasphaltenes are not able to diffuse into the pores of catalyst asreadily as other, smaller molecules in the resid material. As a result,a much higher proportion of asphaltenes remained unconverted, and theremaining unconverted resid material contained an increased proportionof asphaltenes. Producing a resid material having an ever-increasingconcentration of asphaltenes would be expected to lead to catalyst andequipment fouling, which is why only diluted vacuum tower residuum orlow asphaltene feedstocks can be hydroprocessed using conventionalebullated bed and fixed bed systems and at a conversion level less than60.

Example 2

A heavy oil feedstock comprising Athabasca vacuum tower bottoms (whichincluded 21 wt. % of pentane insoluble asphaltenes) from the SyncrudeCanada Ltd. plant in Alberta, Canada, with 150 ppm of a molybdenumsulfide catalyst in colloidal or molecular form was introduced into apilot plant similar to the one shown in FIG. 10 having two gas-liquidslurry phase reactors connected in series. Each reactor had a volume of2200 ml. The first reactor was heated to a weighted averaged temperaturebelow 370° C. (698° F.), and the second reactor was heated to a weightedaveraged temperature between 419-445° C. (786-833° F.) and liquid hourlyspace velocity between 0.41 and 0.7/hr. The results of this test showedthat the concentration of the asphaltene in the residual resid at 75%conversion was also 21 wt. %, which was identical to that in theoriginal feedstock, thereby further confirming the ability of thecolloidal or molecular catalyst to convert the asphaltene fraction atthe same rate as the resid material as a whole.

Example 3

This example tested the ability of a colloidal or molecular catalystutilized in a slurry phase reactor according to the invention to convertvarious resid materials and their asphaltene and sulfur fractions athigh conversion rates. The pilot plant used in this example was the sameslurry phase, tubular reactor described in Example 1. In each test, theheavy oil feedstock was thoroughly mixed with up to 250 parts permillion of the catalyst precursor over a prolonged period of time beforebeing introduced to the reactor. The reactor temperature was maintainedbetween 430-450° C. to control the conversion level. The reactorpressure was 2000 psig and the hydrogen treat rate was 5000 standardcubic feet per barrel of heavy oil. The results of this test are setforth in Table I below:

TABLE I Cold Maya/ Athabasca Lake Isthmus Chinese Paraffinic FeedstockBitumen Bottoms Blend Bottoms Blend 975° F. + resid 94 94 63 95conversion, wt % Asphaltene (C₅ Ins.) 95 93 67 96 conversion wt % Sulfurconversion 78 78 56 92 wt %

This test confirms that a colloidal or molecular catalyst utilized in aslurry phase reactor according to the invention was able to convert theasphaltene fraction at essentially the same rate as the overall residconversion rate, even at very high overall conversion rates. Thisdemonstrates the superiority of the hydroprocessing methods and systemsdisclosed herein compared to conventional fixed bed systems, whichcannot be operated at conversion levels higher than about 25% whenprocessing reside feedstocks having a significant asphaltene fraction,and conventional ebullated bed systems, which convert asphaltenes atsubstantially lower conversion levels compared to overall residconversion, particular at high resid conversion levels. This shows thatthe methods and systems of the invention satisfy a long-felt need in theart that has not been solved using convention hydroprocessing systems(i.e., being able to convert high asphaltene-containing feedstocks athigh conversion levels while also converting the asphaltene fraction atthe same conversion level). It is also a surprising and unexpectedresult given the fact that conventional supported catalysts in existenceand used for decades cannot convert the asphaltene and overall residfractions at the same rate, particularly at high overall conversionlevels.

Example 4

This example utilized the pilot plant shown in FIG. 10, which includedtwo ebullated bed reactors connected in series and which was used tocompare the difference between using a porous supported ebullated bedcatalyst (“EB catalyst”) by itself when processing a heavy oil feedstockcontaining asphaltenes and the EB catalyst in combination with acolloidal or molecular molybdenum disulfide catalyst. Acurrently-operating commercial ebullated bed unit was simulated in thispilot test. The feedstock for this test was a vacuum tower bottomsgenerated from a Russian crude in an operating commercial plant, and theEB catalyst was taken from inventory at the same commercial plant. Thevacuum tower bottoms contained 90 wt. % of material with a boiling pointof 525° C.+ (i.e., greater than or equal to 525° C.). The comparativeexperiments were carried out at reaction temperature between 418-435° C.to control the conversion level, a space velocity of 0.26 per hour, ahydrogen feed rate of 4500 standard cubic feet per barrel of heavy oil,and a pressure of 2100 psig.

The results of this comparative study are graphically depicted in FIGS.11-14. The comparative study demonstrated the ability of the colloidalor molecular catalyst to convert asphaltenes to lower boiling materialswhile also prolonging the useful lifespan of the porous supportedcatalyst.

The first run (Run “A”) was a base-line test simulating the currentcommercial unit operation with the EB catalyst, but without thecolloidal or molecular catalyst. To simulate real commercial conditions,a mixture of one-third fresh EB catalyst and ⅔ equilibrium EB catalysttaken from the commercial plant was used. The test unit was operated for5 days at approximately 50 wt % residuum (b.p.≧524° C.) conversion, andthen for 4 days at 58-60 wt % conversion. At the end of the 9-dayperiod, the test had to be shut down because of a significant increasein pressure across the second reactor schematically shown in FIG. 10. Atthe end of the run, the reactors were opened, the EB catalyst wasunloaded, and the reactor walls and all accessories were inspected.Samples were taken and analyzed.

The second test (Run “B”) was a duplication of Run “A”, using anidentical catalyst charge (i.e., a mixture of fresh and equilibrium EBcatalyst), but with the feedstock conditioned with 25 to 100 ppm of acolloidal or molecular molybdenum sulfide catalyst (i.e., 50 ppm from0-120 hours; 100 ppm from 120-195 hours; 100 ppm from 195-270 hours; 50ppm from 270-340 hours, and 25 ppm beyond 340 hours). After operatingfor 8 days at the same conditions as Run “A”, conversion was increasedto 70% and was held at that level for 3 days. The residuum conversionlevel was then reduced back to 60% and held for 5 days to confirm thereproducibility of the test results. Run “B” was then terminated at theend of this time, with the observation that the unit was fully operablewith no noticeable change in pressure drop across the second reactorshown in FIG. 10, even after 16 days on-stream. As in the first test,the reactors were opened and inspected after shutdown.

The pressure drop across the second reactor that caused the shutdown ofRun “A”, but which did not occur in Run “B”, is graphically depicted inthe chart of FIG. 11. As shown in FIG. 11, Run “A” lasted a little overapproximately 220 hours before it was halted due to a dramatic increasein pressure drop across the second reactor resulting from deposition ofsediment in the reactor (i.e., equipment fouling). A post-run inspectionshowed significant fouling of the screen at the reactor liquid recyclecup of the second reactor, which caused the increase in pressure dropbetween the reactor inlet and outlet. On the other hand, Run “B” lastedabout 400 hours and was only halted because all the relevant data hadbeen obtained, not because of any equipment fouling or pressure increaseacross the second reactor. A post-run inspection showed minimal foulingof the screen at the reactor liquid recycle cup in the second reactor,thus preventing, or at least minimizing, the type of differentialpressure increase that occurred in Run “A”.

The chart shown in FIG. 12 plots resid conversion versus hourson-stream. For the first 9 days, the two test runs tracked each othervery well. Only Run “B” was able to continue more than 9 days, however,as described above. As shown in FIG. 12, when the percent conversion wasmaintained at approximately the same level for both test runs, Run “B”had a substantially higher percent conversion of the resid fraction.This demonstrated that the colloidal or molecular catalyst assisted theEB catalyst in converting the vacuum tower residuum material to lowerboiling materials.

The chart depicted in FIG. 13 shows asphaltene conversion (defined interms of heptane insolubles) versus time on-stream at various residconversion levels. Run “B”, using the colloidal or molecular catalystand EB catalyst, achieved approximately twice the asphaltene conversionas in Run “A”, using the EB catalyst alone. This significant improvementin asphaltene conversion is directly attributable to the use of thecolloidal or molecular catalyst because, otherwise, the two test runswere identical. This test confirms the results of Example 1, whichdemonstrated that a colloidal or molecular catalyst is much better ableto convert asphaltenes in a heavy oil feedstock than a porous supportedcatalyst.

The chart depicted in FIG. 14 plots percent desulfurization of theresiduum as a function of time comparing Run “A” using just the EBcatalyst and Run “B” using both the EB catalyst and the colloidal ormolecular catalyst.

Table II below summarizes the test data on sediment formation asdetermined by the IP 375 Method.

TABLE II IMPACT OF COLLOIDAL OR MOLECULAR CATALYST ON SEDIMENT FORMATIONAND FOULING Residuum conversion 50 60 71 60 wt. % Time On-Stream hours 0 to 132 133 to 220 204 to 272 272 to 400 RUN “A”: Sediment 0.12-0.220.59-0.86 N/A N/A wt. % (EB catalyst only) RUN “B”: Sediment 0.06-0.150.32-0.36 0.72-1.06 0.23-0.35 wt. % (EB catalyst + C or M catalyst) RunA operated for 220 hours but had to be stopped when the differentialpressure in the second reactor increased significantly. No data wasgenerated after 220 hours. A post-run inspection showed significantlyfouling on the screen of the reactor liquid recycle cup. Run B operatedfor 400 hours with very little change in reactor differential pressure.Inspection showed the screen at the reactor liquid recycle cup to beclean with minimal fouling.

The sediment formation values for Run “B” were about half of those fromRun “A” during the comparative time periods and reaction conditions. ForRun “B”, when conversion was reduced from 71% to 60% in the last 5 days,sediment values returned to the same range as in the initial 60%conversion, despite any additional EB catalyst deactivation that mayhave occurred when operating the reactor at 71% conversion. Becausesediment was significantly reduced when the colloidal or molecularcatalyst was used, the pilot plant unit proved to be less prone tofouling and plugging than when just the conventional EB catalyst wasused, as evidenced by the lower pressure drop across the reactor. It canbe extrapolated that the same benefits of using the colloidal ormolecular catalyst would apply in commercial-scale operations. That is,reduced sediment formation would be expected to lead to less fouling ofthe equipment and solid supported catalyst which, in turn, would resultin longer unit operation and less maintenance when the colloidal ormolecular catalyst is used in addition to, or in combination with, theEB catalyst.

In summary, the colloidal or molecular catalyst consistently increasedthe asphaltene conversion in parallel with the resid conversion andreduced sediment formation. These results demonstrate that the colloidalor molecular catalyst significantly increased hydrogen transfer outsidethe supported catalyst, capped the free radicals, and minimizedcombination reactions involving free radicals, as reflected in thereduction of sediment at all levels of resid conversion. Reducingsediment formation reduces rate of deactivation of the supportedcatalyst. The supported catalyst is therefore able to continue toperform its catalytic function of removing sulfur and transferringhydrogen, resulting in higher API gravity products.

Example 5

A test was conducted using the pilot plant describes in FIG. 10, exceptthat the first and second reactors were operated in a slurry phasehydroprocessing system comprising a slurry phase reactor that utilized125 parts per million of a colloidal or molecular molybdenum disulfidecatalyst. (The reactors operated as “slurry phase” reactors in this testrather than ebullated bed reactors because they utilized no poroussupported ebullated bed catalyst). The pilot plant operated at 1500 psigof hydrogen pressure, with the conditioned Athabasca resid being fed ata space velocity of 0.7 per hour, a hydrogen treat rate at 4500 standardcubic feet per barrel of resid, within the first reactor beingmaintained at less than 370° C. and the second reactor being maintainedat 441° C. The liquid product was collected and fed into a simulatedguard bed reactor packed with a demetalizing catalyst.

The purpose of this test was to determine whether a slurry phase reactoremploying a colloidal or molecular molybdenum disulfide catalyst couldbe used to preliminarily convert resid and asphaltene fractions, as wellas metals contained therein to metal sulfides, followed by removing anymetal sulfides, including the colloidal or molecular molybdenumdisulfide catalyst by the guard bed. This would allow a fixed bedreactor to subsequently carry out desulfurization and denitrogenation ofthe preliminarily converted feedstock without the risk of plugging thehydrotreating catalyst by metals originally in the feedstock and/or fromthe added colloidal or molecular molybdenum disulfide catalyst.

In this study, a catalyst precursor composition comprising molybdenum2-ethylhexanoate (15% molybdenum by weight) was first diluted down toabout 1% by weight molybdenum metal using Number 2 fuel oil (heavydiesel). This diluted precursor composition was intimately mixed withAthabasca vacuum tower bottoms to yield a conditioned feedstock, whichwas heated to 400° C. (752° F.) in a feed heater to form the colloidalor molecular molybdenum disulfide catalyst and then hydrocracked at 440°C. (824° F.) in a pilot gas-liquid slurry phase back-mixed reactor.

The second reactor shown in FIG. 10 had an effective volume of 2,239 ml,a height of 4.27 meters, and an internal diameter of 2.95 cm. The pilotreactor had an external recycle pump to circulate the reactor liquidfrom the top of the reactor back to the reactor entrance by means of anexternal loop. Circulating the reactor liquid enabled rapid dissipationof heat generated by hydroprocessing reactions and maintenance of ahomogeneous reactor liquid temperature profile. At the reactor entrance,fresh feedstock and hydrogen were joined with the recycled reactorliquid, which then underwent hydrocracking reactions.

Effluent taken from the reactor was introduced into a hot separator,which separated the effluent into a hot vapor and gaseous stream, whichwas removed from the top, and a liquid product stream, which was removedfrom the bottom. After cooling and pressure reduction through subsequentdownstream separators, the hydrocracked products were collected as lightcondensates, bottom liquid, product gas, and dissolved gas. The lightcondensate and bottom liquid were combined as total liquid and fed tothe guard bed reactor packed with a commercial demetalization catalystsupplied by WR Grace.

140 grams of demetalization catalyst were utilized within the guard bedunit. The feed rate was 124 g/hr of hydrocracked product from the slurryphase reactor. Operating conditions were 380° C. (716° F.) at 2,000 psi.The hydrogen flow rate was 300 SCF/bbl (standard cubic feet perbarrel—42 gallons of liquid feed). The metal analysis of thehydrocracked product from the pilot slurry phase reactor are shown inTable III as follows:

TABLE III Concentration Metal (Weight Part Per Million (WPPM)) Nickel 94Vanadium 260 Molybdenum 134

The metal analysis after the product was demetalized using the guard beddemetalization catalyst is shown in Table IV as follows:

TABLE IV Metal WPPM Wt % Removed Nickel 4 95.7 Vanadium 5 98.1Molybdenum 4 97.0

As plainly shown, fixed bed demetalization resulted in the removal ofthe vast majority of metals from the upgraded feedstock formed using thecolloidal or molecular catalyst within the pilot slurry phase reactor.This shows that preliminary upgrading of a heavy oil feedstock using acolloidal or molecular catalyst can be successfully carried out in orderto (i) upgrade asphaltenes and other higher boiling resid hydrocarbonsand (ii) convert metals into a form that facilitates their removal byguard bed demetalization so as to prevent fouling of a downstream fixedbed hydrotreating reactor used for desulfurization and denitrogenation.The demetalization catalyst removed both the colloidal or molecularmolybdenum disulfide catalyst and the nickel and vanadium fraction foundin the feedstock at about the same rate, thereby demonstrating that thecolloidal or molecular catalyst could be removed using the samedemetalization process typically used to remove metal contaminants froma feedstock. In view of this, one of skill in the art would expect thatpreliminary upgrading of a heavy oil feedstock rich in asphaltenes canbe carried out upstream of a fixed bed hydroprocessing reactor using acolloidal or molecular catalyst, e.g., in one or more of a slurry phasereactor or an ebullated bed reactor, followed by demetalization in aguard bed, in order to eliminate or greatly reduce fouling of adownstream hydrotreating fixed bed reactor by asphaltenes and/or metalsfound in the feedstock.

Example 6

A pilot plant with two ebullated bed reactors connected in series wasused to compare the difference between using a porous supportedebullated bed catalyst (“EB catalyst”) by itself when processing a heavyoil feedstock containing asphaltenes and the EB catalyst in combinationwith a colloidal or molecular molybdenum disulfide catalyst. The pilotplant 900 for this test is schematically depicted in FIG. 10, andincluded a high shear mixing vessel 902 used to blend molybdenum2-ethylhexanoate (15% molybdenum by weight of the catalyst precursorcomposition) into the feedstock to form a conditioned feedstock. Thefeedstock for this test was 95% Athabasca resid and 5% decant oil froman operating commercial plant, and the EB catalyst was taken frominventory at the same commercial plant. The conditioned feedstock wascirculated out and back into the mixing vessel 902 by a pump 904. A highprecision metering piston pump 906 drew the conditioned feedstock fromthe loop and pressurized it to the reactor pressure. Thereafter,hydrogen 908 was fed into the pressurized feedstock and the resultingmixture passed through a pre-heater 910 prior to being introduced intothe first of two pilot slurry phase/ebullated bed reactors 912.

Each of reactors 912, 912′ had an interior volume of 2200 ml andincluded a porous supported catalyst and a mesh wire guard 914 to keepthe supported catalyst within the reactor. The settled height ofcatalyst in each reactor is indicated by a lower dotted line 916, andthe expanded catalyst bed during use is indicated by an upper dottedline 918. The first reactor was loaded with equilibrium catalyst fromthe second of two LC-Fining reactors in series, while the second reactorwas loaded with ⅓ fresh catalyst and ⅔ equilibrium catalyst from theLC-Fining reactor. The reactors 912, 912′ were operated at a spacevelocity of 0.28 reactor volume per hour with 2100 psig back pressure.The rate of hydrogen feed was 4500 scf/barrel, with 60% being introducedinto the first reactor 912 and 40% being added as supplemental hydrogen920 to the material being transferred from the first reactor 912 to thesecond reactor 912′.

During use, either the feedstock only (in the case of Run “A” using anebullated bed catalyst only) or the feedstock and colloidal or molecularcatalyst (in the case of Run “B” using an ebullated bed catalyst and thecolloidal or molecular catalyst) were continuous recycled from the topof each reactor to the bottom of the reactor in a manner similar to anactual commercial ebullated bed reactor as it was being upgraded.Upgraded feedstock from the first reactor 912 was transferred togetherwith supplemental hydrogen into the second reactor 912′ for furtherhydroprocessing. The further upgraded material from the second reactor912′ was introduced into a first hot separator 922 to separate gases andvapors 924 from a liquid fraction. The liquid 926 from the first hotseparator was introduced into a second hot separator 928 to removeadditional gases and vapors 924′, which were blended with those from thefirst hot separator 922 and then separated into gases 930 and condensate932. The hot separator bottoms 934 were removed from the second hotseparator 928.

The first run (Run “A”) was a base-line test simulating the currentcommercial unit operation with the EB catalyst, but without thecolloidal or molecular catalyst. The second test (Run “B”) was aduplication of Run “A”, using an identical catalyst charge (i.e., amixture of fresh and equilibrium EB catalyst), but with the feedstockconditioned with 50 parts per million of a molybdenum sulfide colloidalor molecular catalyst. For each run, the test unit was operated for 5days at a reactor temperature of 425° C., followed by 4 days at atemperature of 432-434° C., and then 1 day at 440° C. Samples were takenfrom the hot separator bottoms at the end of each 24-hour period andtested.

The results of this comparative study are graphically depicted in FIGS.15-22. The comparative study demonstrated the ability of the colloidalor molecular catalyst to convert asphaltenes to lower boiling materialswhile also reducing the formation of sediment in the reactors. Itfurther confirmed the results of the examples above showing that theasphaltene fraction can be converted at the same rate as the overallresid material.

The chart shown in FIG. 15 plots the pressure drop across the secondreactor for each of Runs “A” and “B” throughout the duration of thetest. The chart shown in FIG. 16 plots resid conversion for Runs “A” and“B” versus hours on stream. Throughout the test, the overall conversionlevels for the two types of catalysts were kept about the same.Nevertheless, the chart shown in FIG. 15 shows a greater pressure dropacross the second reactor for Run “A” compared to Run “B” throughout thetest after the first 24 hours. The greater pressure differentialsuggests a significantly larger buildup of sediment in the reactorsduring Run “A” than in Run “B”, which is consistent with lowerconversion of asphaltenes in Run “A”.

In fact, the chart depicted in FIG. 17 shows that the asphalteneconversion (defined in terms of heptane (C₇) insolubles) versus timeon-stream at various resid conversion levels was substantially higher inRun “B” compared to Run “A”. The asphaltene conversion levels for eachof Runs “A” and “B” started out relative high. Thereafter, theasphaltene conversion for Run “B” remained high (i.e., greater thanabout 85%, while the asphaltene conversion for Run “A” progressivelydropped as the test continued. Moreover, the difference between theasphaltene conversion levels for Runs “A” and “B” progressively widenedas the test progressed. This demonstrates that the colloidal ormolecular catalyst greatly assisted in converting the asphaltenefraction, particularly over time, compared to using the porous supportedcatalyst by itself.

The chart depicted in FIG. 18 plots the API gravity of the hot separatorbottoms for Runs “A” and “B”. The chart depicted in FIG. 19 plots theunconverted resid API gravity for Runs “A” and “B”. The data in bothcharts are consistent with the overall increase in asphaltene conversionin Run “B” compared to Run “A” and increased hydrogen transfer to theproduct via the colloidal or molecular catalyst and the less deactivatedporous supported catalyst. The reduction in sediment formation slows thedeactivation of the supported catalyst, which is clearly demonstrated bythe higher API gravity shown in FIGS. 18 and 19. Since API gravity isdirectly related to quality and hydrogen contents, higher API gravitymeans higher hydrogen contents and lower absolute specific gravity.

The chart shown in FIG. 20 plots the IP-375 sediment found in the hotseparator bottoms for each of Runs “A” and “B”. The chart depicted inFIG. 21 plots the percentage of asphaltenes found in the hot separatorbottoms for each of Runs “A” and “B”. The 2-3 fold increase in sedimentfound in the hot separator bottoms produced in Run “A” compared to Run“B” is consistent with the greater concentration of asphaltenes found inthe hot separator bottoms from Run “A”. Moreover, while theconcentration of asphaltenes found in the hot separator bottoms from Run“B” remained substantially constant throughout the test, the asphaltenesfound in the hot separator bottoms from Run “A” progressively increasedover time. This shows that using the colloidal or molecular catalystwould be expected to greatly assist in maintaining steadier levels ofasphaltenes in the processed feedstocks, with an attendant reduction insediment formation compared to using a porous supported catalyst byitself.

The chart in FIG. 22 plots the weight percent of micro carbon residue(MCR) found in the hot separator bottoms for each of Runs “A” and “B”.Consistent with the previous data, the MCR in the hot separator bottomsfor Run “B” increased throughout the test, while it initially increasedthen stagnated throughout Run “A”.

The benefits of adding the colloidal or molecular catalyst in additionto the porous supported ebullated bed catalyst compared to using theebullated bed catalyst by itself can be seen by the follow additionaldata gleaned from the foregoing test set forth in Table V:

TABLE V EB Cat. + C or M Catalyst EB Catalyst Cat. Change 525° C. +Conv. wt % 72.8 81.7 8.9 C₁-C₃, wt % feed 3.9 5.3 1.4 C₄-524° C. Barrel0.77 (34.1° API) 0.88 (36.9° API) 0.11 (2.8° API) product/Barrel feed525° C.+, Barrel 0.25 (5.8° API)  0.16 (4.3° API)  −0.09 (−1.5° API)product/Barrel feed Conradson Carbon 69.3 76.4 7.1 residue or MCRConversion C₇ Asph Conv wt % 79.8 88.4 8.6 Sediment after hot 0.03 <0.01−0.02 filtration test following the blending of 525° C.+ resid with alight crude oil Basic Sediment and 0.2 0.1 −0.1 Water content

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. An ebullated bed hydroprocessing system, comprising: an ebullated bedreactor comprised of: an expanded catalyst bed comprising a poroussupported catalyst as a solid phase; an upper region above the expandedcatalyst bed that is devoid of the porous supported catalyst; a lowerregion below the expanded catalyst bed that is devoid of the poroussupported catalyst; a liquid hydrocarbon phase comprised of a heavy oilfeedstock within the expanded catalyst bed, the upper region, and thelower region; a colloidal or molecular catalyst having a particle sizeless than about 100 nm dispersed throughout the liquid hydrocarbonphase; and a gaseous phase comprised of hydrogen gas dispersed in theliquid hydrocarbon phase; mixing apparatus for intimately mixing acatalyst precursor composition with a hydrocarbon oil diluent at atemperature below which the catalyst precursor composition decomposes inorder to form a diluted precursor mixture comprised of the hydrocarbonoil diluent and the catalyst precursor composition; blending apparatuspositioned upstream of the ebullated bed reactor for blending thediluted precursor mixture with the heavy oil feedstock to form aconditioned feedstock in which the catalyst precursor composition issufficiently well dispersed within the heavy oil feedstock so as to formthe colloidal or molecular catalyst in situ upon heating anddecomposition of the catalyst precursor composition; and heating meansfor heating the conditioned feedstock in order to decompose the catalystprecursor composition and form the colloidal or molecular catalyst insitu within the heavy oil feedstock.
 2. An ebullated bed hydroprocessingsystem as defined in claim 1, wherein the heavy oil feedstock within theexpanded catalyst bed, the upper region, and the lower region is at ahydrocracking temperature.
 3. An ebullated bed hydroprocessing system asdefined in claim 1, wherein the blending apparatus is configured tointimately mix the diluted precursor mixture containing the catalystprecursor composition into the heavy oil feedstock to further reduce theparticle size of the colloidal or molecular catalyst.
 4. An ebullatedbed hydroprocessing system as defined in claim 1, wherein the heatingmeans is positioned upstream of the ebullated bed reactor.
 5. Anebullated bed hydroprocessing system as defined in claim 1, wherein theheating means at least partially comprises the ebullated bed reactor. 6.An ebullated bed hydroprocessing system as defined in claim 1, whereinthe catalyst precursor composition comprises an organo-metallic compoundor complex.
 7. An ebullated bed hydroprocessing system as defined inclaim 1, the catalyst precursor composition comprising at least onetransition metal and at least one organic moiety comprising or derivedfrom octanoic acid, 2-ethylhexanoic acid, naphthanic acid,pentacarbonyl, or hexacarbonyl.
 8. An ebullated bed hydroprocessingsystem as defined in claim 1, the catalyst precursor compositioncomprising at least one of molybdenum 2-ethylhexanoate, molybdenumnaphthanate, molybdenum hexacarbonyl, vanadium octoate, vanadiumnaphthanate, or iron pentacarbonyl.
 9. An ebullated bed hydroprocessingsystem as defined in claim 1, wherein the hydrocarbon oil diluentcomprises at least one of vacuum gas oil, decant oil, cycle oil, orlight gas oil.
 10. An ebullated bed hydroprocessing system as defined inclaim 1, the mixing apparatus being configured to yield a ratio of thecatalyst precursor composition to the hydrocarbon oil diluent in a rangeof about 1:500 to about 1:1.
 11. An ebullated bed hydroprocessing systemas defined in claim 1, the colloidal or molecular catalyst comprising atleast one transition metal site donated by the catalyst precursorcomposition and at least one sulfur site donated by the heavy oilfeedstock.
 12. An ebullated bed hydroprocessing system as defined inclaim 11, the colloidal or molecular catalyst comprising individualmetal sulfide catalyst molecules and/or colloidal-sized catalystparticles of metal sulfide.
 13. An ebullated bed hydroprocessing systemas defined in claim 1, the colloidal or molecular catalyst providingcatalyst metal having a concentration in a range of about 10 ppm toabout 500 ppm by weight of the heavy oil feedstock.
 14. An ebullated bedhydroprocessing system as defined in claim 1, further comprising ahydrocracking reactor positioned upstream from the ebullated bed reactorand downstream from the blending apparatus.
 15. An ebullated bedhydroprocessing system as defined in claim 14, the hydrocracking reactorcomprising a slurry phase reactor containing a liquid phase comprised ofa heavy oil feedstock and a molecular or colloidal catalyst and agaseous phase comprised of hydrogen gas.
 16. An ebullated bedhydroprocessing system as defined in claim 15, the slurry phase reactorcomprising a former ebullated bed reactor that was converted into theslurry phase reactor by removing the supported catalyst from the formerebullated bed reactor.
 17. An ebullated bed hydroprocessing system asdefined in claim 15, the slurry phase reactor comprising a recyclechannel, recycling pump, and a distributor grid plate.
 18. An ebullatedbed hydroprocessing system, comprising: an ebullated bed reactorcomprised of: an expanded catalyst bed comprising a porous supportedcatalyst as a solid phase; an upper region above the expanded catalystbed that is devoid of the porous supported catalyst; a lower regionbelow the expanded catalyst bed that is devoid of the porous supportedcatalyst; a liquid hydrocarbon phase comprised of a heavy oil feedstockwithin the expanded catalyst bed, the upper region, and the lowerregion; a colloidal or molecular catalyst having a particle size lessthan about 100 nm dispersed throughout the liquid hydrocarbon phase; anda gaseous phase comprised of hydrogen gas dispersed in the liquidhydrocarbon phase; mixing apparatus for intimately mixing a catalystprecursor composition with a hydrocarbon oil diluent at a temperaturebelow which the catalyst precursor composition decomposes in order toform a diluted precursor mixture comprised of the hydrocarbon oildiluent and the catalyst precursor composition; blending apparatuspositioned upstream of the ebullated bed reactor for blending thediluted precursor mixture with the heavy oil feedstock at a temperaturebelow which the catalyst precursor composition is completely decomposedto form a conditioned feedstock in which the catalyst precursorcomposition is sufficiently well dispersed within the heavy oilfeedstock so as to form the colloidal or molecular catalyst in situ uponheating and decomposition of the catalyst precursor composition; heatingmeans positioned upstream of the ebullated bed reactor for heating theconditioned feedstock in order to decompose the catalyst precursorcomposition and form the colloidal or molecular catalyst in situ withinthe heavy oil feedstock; and means for introducing the heavy oilfeedstock containing the colloidal or molecular catalyst into theebullated bed reactor.
 19. An ebullated bed hydroprocessing system asdefined in claim 18, wherein the blending apparatus is configured tointimately mix the diluted precursor mixture containing the catalystprecursor composition into the heavy oil feedstock in order for theparticle size of the colloidal or molecular catalyst to be less thanabout 10 nm.
 20. An ebullated bed hydroprocessing system as defined inclaim 18, wherein the hydrocarbon oil diluent comprises at least one ofvacuum gas oil, decant oil, cycle oil, or light gas oil.
 21. Anebullated bed hydroprocessing system as defined in claim 18, the mixingapparatus being configured to yield a ratio of the catalyst precursorcomposition to the hydrocarbon oil diluent in a range of about 1:500 toabout 1:1.
 22. An ebullated bed hydroprocessing system as defined inclaim 18, the colloidal or molecular catalyst providing catalyst metalhaving a concentration in a range of about 10 ppm to about 500 ppm byweight of the heavy oil feedstock.
 23. An ebullated bed hydroprocessingsystem as defined in claim 18, further comprising a hydrocrackingreactor positioned upstream from the ebullated bed reactor.
 24. Anebullated bed hydroprocessing system as defined in claim 23, thehydrocracking reactor comprising an ebullated bed reactor, fixed bedreactor or slurry phase reactor.
 25. An ebullated bed hydroprocessingsystem, comprising: an ebullated bed reactor comprised of: an expandedcatalyst bed comprising a porous supported catalyst as a solid phase; anupper region above the expanded catalyst bed that is devoid of theporous supported catalyst; a lower region below the expanded catalystbed that is devoid of the porous supported catalyst; a liquidhydrocarbon phase comprised of a heavy oil feedstock within the expandedcatalyst bed, the upper region, and the lower region; a colloidal ormolecular catalyst dispersed throughout the liquid hydrocarbon phase;and a gaseous phase comprised of hydrogen gas dispersed in the liquidhydrocarbon phase; mixing apparatus for intimately mixing a catalystprecursor composition with a hydrocarbon oil diluent at a temperaturebelow which the catalyst precursor composition decomposes in order toform a diluted precursor mixture comprised of the hydrocarbon oildiluent and the catalyst precursor composition; blending apparatuspositioned upstream of the ebullated bed reactor for blending thediluted precursor mixture with the heavy oil feedstock prior toformation of the colloidal or molecular catalyst to form a conditionedfeedstock in which the catalyst precursor composition is sufficientlywell dispersed within the heavy oil feedstock so as to form thecolloidal or molecular catalyst in situ upon heating and decompositionof the catalyst precursor composition; and heating means for heating theconditioned feedstock in order to decompose the catalyst precursorcomposition and form the colloidal or molecular catalyst in situ withinthe heavy oil feedstock.